Authentication system and method for recording unlocking history using authentication system

ABSTRACT

A novel authentication system is provided. In addition, a method for recording an unlocking history is provided. The authentication system includes an arithmetic device and an input/output device. The arithmetic device supplies first control data and second control data, and is supplied with a sensor signal. The input/output device includes an electric lock and a reading portion, and the electric lock is unlocked on the basis of the second control data. The reading portion is supplied with the first control data, supplies the sensor signal, and includes a light-emitting element and a pixel array. The light-emitting element emits light including infrared rays, the pixel array includes pixels, the pixels each include an imaging circuit and a photoelectric conversion element, the imaging circuit is electrically connected to the photoelectric conversion element, the imaging circuit includes a transistor, and the transistor includes an oxide semiconductor film.

TECHNICAL FIELD

One embodiment of the present invention relates to an authenticationsystem or a method for recording an unlocking history using theauthentication system.

Note that one embodiment of the present invention is not limited to theabove technical field. The technical field of one embodiment of theinvention disclosed in this specification and the like relates to anobject, a method, or a manufacturing method. One embodiment of thepresent invention relates to a process, a machine, manufacture, or acomposition of matter. Thus, more specifically, examples of thetechnical field of one embodiment of the present invention disclosed inthis specification include a semiconductor device, a display device, alight-emitting device, a power storage device, a memory device, adriving method thereof, and a manufacturing method thereof.

BACKGROUND ART

An authentication device for living body communication that performsauthentication by communication via a living body with a terminal devicefor living body communication worn on a living body is known (PatentDocument 1).

The authentication device for living body communication includes anelectric lock for communication provided to be proximate to a livingbody; a transmitting circuit that transmits a startup signal through acommunication electrode; a receiving circuit that receives a receptionsignal including an individual identification ID through thecommunication electrode; a proximity determining portion that determineswhether a living body is proximate to the communication electrode on thebasis of the reception signal level at a timing when the startup signalis intermittently transmitted through the receiving circuit portion; anda comparing portion that compares on the basis of the individualidentification ID, and is provided with an authentication controlportion that allows authentication when a living body is determined tobe proximate and the comparison result is verified.

REFERENCE Patent Document

[Patent Document 1] Japanese Published Patent Application No.2011-101095

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

An object of one embodiment of the present invention is to provide anauthentication system that is highly convenient or reliable. Anotherobject is to provide a method for recording an unlocking history, whichis highly convenient or reliable. Another object is to provide a novelauthentication system, a novel method for recording an unlockinghistory, or a novel semiconductor device.

Note that the descriptions of these objects do not preclude theexistence of other objects. One embodiment of the present invention doesnot have to achieve all these objects. Objects other than these areapparent from the descriptions of the specification, the drawings, theclaims, and the like, and objects other than these can be derived fromthe descriptions of the specification, the drawings, the claims, and thelike.

Means for Solving the Problems

One embodiment of the present invention is an authentication systemincluding an arithmetic device and an input/output device.

The arithmetic device supplies a first control data and a second controldata, and the arithmetic device is supplied with a sensor signal.

The input/output device includes an electric lock and a reading portion.

The electric lock is unlocked on the basis of the second control data.The reading portion is supplied with the first control data and suppliesthe sensor signal, and the reading portion includes a light-emittingelement and a pixel array.

The light-emitting element emits light including infrared rays, thepixel array includes pixels, and the pixels each include an imagingcircuit and a photoelectric conversion element.

The imaging circuit is electrically connected to the photoelectricconversion element, and the imaging circuit includes a transistor. Thetransistor includes an oxide semiconductor film, and the photoelectricconversion element includes an organic semiconductor film.

Thus, an image of a physical feature can be taken, for example.Alternatively, an image of a vein spread or a vein arrangement patterncan be taken, for example. Alternatively, data included in a physicalfeature can be extracted. Alternatively, a security level can beincreased. As a result, a novel authentication system that is highlyconvenient or reliable can be provided.

Another embodiment of the present invention is the authentication systemin which the above arithmetic device includes an arithmetic portion anda memory portion.

The memory portion stores a program and a first database.

The arithmetic portion extracts a feature value from the sensor signalon the basis of the program, and the arithmetic portion examines thefeature value using the first database.

The arithmetic portion supplies the second control data on the basis ofthe examination result.

In this manner, an individual having a predetermined physical featurecan be authenticated. Alternatively, the security level can beincreased. As a result, a novel authentication system that is highlyconvenient or reliable can be provided.

Another embodiment of the present invention is the authentication systemin which the above memory portion stores a second database.

The arithmetic portion records an unlocking history in the seconddatabase on the basis of the examination result.

Accordingly, the unlocking history can be recorded. Alternatively, theunlocking history can be recorded in association with an individualhaving a predetermined physical feature. Alternatively, the securitylevel can be increased. As a result, a novel authentication system thatis highly convenient or reliable can be provided.

Another embodiment of the present invention is the authentication systemin which the above pixel includes a first layer and a second layer.

The first layer includes a first transistor and a second transistor, andthe second layer includes a light-emitting element and a photoelectricconversion element.

One of a source and a drain of the first transistor is electricallyconnected to one electrode of the light-emitting element, and one of asource and a drain of the second transistor is electrically connected toone electrode of the photoelectric conversion element.

Another embodiment of the present invention is the authentication systemin which the above oxide semiconductor film contains In, Zn, and M (M isAl, Ti, Ga, Sn, Y, Zr, La, Ce, Nd, or Hf).

Thus, the number of optical components such as a lens can be reduced.Alternatively, the thickness can be made small. Alternatively,wide-range imaging can be performed. Furthermore, the area can be easilyincreased. Alternatively, an image of a proximate subject can becaptured. Alternatively, high-resolution imaging can be performed. As aresult, a novel authentication system that is highly convenient orreliable can be provided.

Another embodiment of the present invention is a method for recording anunlocking history including a first step to a seventh step.

In the first step, imaging is performed to obtain a sensor signal.

In the second step, a program proceeds to the third step in the casewhere a change exceeding a predetermine level is observed in the sensorsignal, and the program proceeds to the first step in the case whereonly a change less than or equal to the predetermined level is observed.

In the third step, imaging is performed to obtain a sensor signal.

In the fourth step, a feature value is extracted from the sensor signal.

In the fifth step, the feature value is examined using a first database.The program proceeds to the sixth step in the case where the firstdatabase includes data matching the feature value, and the programproceeds to the first step in the case where the first database includesno data matching the feature value.

In the sixth step, second control data is supplied to unlock an electriclock.

In the seventh step, the unlocking history is recorded in a seconddatabase.

In this manner, the unlocking history can be recorded in the seconddatabase. Alternatively, the unlocking history can be recorded inassociation with an individual having a predetermined physical feature.Alternatively, the security level can be increased. As a result, a novelmethod for recording an unlocking history, which is highly convenient orreliable, can be provided.

Although the block diagram in which components are classified by theirfunctions and shown as independent blocks is shown in the drawingsattached to this specification, it is difficult to completely divideactual components according to their functions and one component canrelate to a plurality of functions.

In this specification, the names of a source and a drain of a transistorinterchange with each other depending on the polarity of the transistorand the levels of potentials applied to the terminals. In general, in ann-channel transistor, a terminal to which a lower potential is appliedis called a source, and a terminal to which a higher potential isapplied is called a drain. In a p-channel transistor, a terminal towhich a lower potential is applied is called a drain, and a terminal towhich a higher potential is applied is called a source. In thisspecification, for the sake of convenience, the connection relation of atransistor is sometimes described assuming that the source and the drainare fixed; in reality, the names of the source and the drain interchangewith each other according to the above relation of the potentials.

In this specification, a source of a transistor means a source regionthat is part of a semiconductor film functioning as an active layer or asource electrode connected to the above semiconductor film. Similarly, adrain of a transistor means a drain region that is part of the abovesemiconductor film or a drain electrode connected to the semiconductorfilm. Moreover, a gate means a gate electrode.

In this specification, a state in which transistors are connected inseries means, for example, a state in which only one of a source and adrain of a first transistor is connected to only one of a source and adrain of a second transistor. In addition, a state in which transistorsare connected in parallel means a state in which one of a source and adrain of a first transistor is connected to one of a source and a drainof a second transistor and the other of the source and the drain of thefirst transistor is connected to the other of the source and the drainof the second transistor.

In this specification, connection means electrical connection andcorresponds to a state in which a current, a voltage, or a potential canbe supplied or transmitted. Accordingly, a state of being connected doesnot necessarily mean a state of being directly connected and alsoincludes, in its category, a state of being indirectly connected througha circuit element such as a wiring, a resistor, a diode, or a transistorthat allows a current, a voltage, or a potential to be supplied ortransmitted.

In this specification, even when independent components are connected toeach other in a circuit diagram, there is actually a case where oneconductive film has functions of a plurality of components such as acase where part of a wiring functions as an electrode, for example.Connection in this specification also includes such a case where oneconductive film has functions of a plurality of components, in itscategory.

Furthermore, in this specification, one of a first electrode and asecond electrode of a transistor refers to a source electrode and theother refers to a drain electrode.

Effect of the Invention

According to one embodiment of the present invention, a novelauthentication system that is highly convenient or reliable can beprovided. Alternatively, a novel method for recording unlocking history,which is highly convenient or reliable, can be provided. Alternatively,a novel authentication system, a novel method for recording unlockinghistory, or a novel semiconductor device can be provided.

Note that the descriptions of the effects do not preclude the existenceof other effects. Note that one embodiment of the present invention doesnot have to have all these effects. Effects other than these will beapparent from the descriptions of the specification, the drawings, theclaims, and the like and effects other than these can be derived fromthe descriptions of the specification, the drawings, the claims, and thelike.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A to FIG. 1E are diagrams illustrating a structure of anauthentication system of one embodiment.

FIG. 2 is a diagram showing a method for recording an unlocking historyusing an authentication system of one embodiment.

FIG. 3 is a diagram illustrating a structure example of a semiconductordevice.

FIG. 4A and FIG. 4B are diagrams each illustrating a structure exampleof a semiconductor device.

FIG. 5A to FIG. 5D are diagrams illustrating an example of a fabricationmethod of a semiconductor device.

FIG. 6A to FIG. 6C are diagrams illustrating an example of a fabricationmethod of a semiconductor device.

FIG. 7A and FIG. 7B are diagrams illustrating an example of afabrication method of a semiconductor device.

FIG. 8A to FIG. 8C are diagrams illustrating structure examples of alight-emitting element.

FIG. 9 is a diagram illustrating a structure example of a semiconductordevice.

FIG. 10A and FIG. 10B are diagrams each illustrating a structure exampleof a semiconductor device.

FIG. 11 is a diagram illustrating a structure example of a semiconductordevice.

FIG. 12 is a diagram illustrating a configuration example of a pixel.

FIG. 13A and FIG. 13B are diagrams each illustrating a configurationexample of a semiconductor device.

FIG. 14A is a diagram illustrating a rolling shutter system and FIG. 14Bis a diagram illustrating a global shutter system.

FIG. 15 is a diagram illustrating a configuration example of a pixel.

FIG. 16 is a diagram illustrating a configuration example of asemiconductor device.

FIG. 17 is a diagram showing an example of an operation method of asemiconductor device.

FIG. 18A to FIG. 18D are diagrams illustrating structure examples of atransistor.

FIG. 19A to FIG. 19C are diagrams each illustrating an electronicdevice.

FIG. 20 is a diagram illustrating a market image.

MODE FOR CARRYING OUT THE INVENTION

An authentication system of one embodiment of the present inventionincludes an arithmetic device and an input/output device. The arithmeticdevice supplies a first control data and second control data, and issupplied with a sensor signal. The input/output device includes anelectric lock and a reading portion, and the electric lock is unlockedon the basis of the second control data. The reading portion is suppliedwith the first control data, supplies the sensor signal, and includes alight-emitting element and a pixel array. The light-emitting elementemits light including infrared rays, the pixel array includes pixels,the pixels each include an imaging circuit and a photoelectricconversion element, the imaging circuit is electrically connected to thephotoelectric conversion element, the imaging circuit includes atransistor, and the transistor includes an oxide semiconductor film. Thephotoelectric conversion element includes an organic semiconductor film.

Thus, an image of a physical feature can be taken, for example.Alternatively, an image of a vein spread or a vein arrangement patterncan be taken, for example. Alternatively, data included in a physicalfeature can be extracted. Alternatively, a security level can beincreased. As a result, a novel authentication system that is highlyconvenient or reliable can be provided.

Embodiments will be described in detail with reference to the drawings.Note that the present invention is not limited to the followingdescriptions, and it will be readily appreciated by those skilled in theart that modes and details of the present invention can be modified invarious ways without departing from the spirit and scope of the presentinvention. Thus, the present invention should not be construed as beinglimited to the descriptions in the following embodiments.

Note that in structures of the present invention described below, thesame portions or portions having similar functions are denoted by thesame reference numerals in different drawings, and a description thereofis not repeated. Furthermore, the same hatch pattern is used for theportions having similar functions, and the portions are not especiallydenoted by reference numerals in some cases.

The position, size, range, or the like of each component illustrated indrawings does not represent the actual position, size, range, or thelike in some cases for easy understanding. Therefore, the disclosedinvention is not necessarily limited to the position, size, range, orthe like disclosed in the drawings.

Note that the term “film” and the term “layer” can be interchanged witheach other depending on the case or circumstances. For example, the term“conductive layer” can be changed into the term “conductive film”. Asanother example, the term “insulating film” can be changed into the term“insulating layer”.

In this specification and the like, a metal oxide is an oxide of metalin a broad sense. Metal oxides are classified into an oxide insulator,an oxide conductor (including a transparent oxide conductor), an oxidesemiconductor (also simply referred to as an OS), and the like. Forexample, in the case where a metal oxide is used in a semiconductorlayer of a transistor, the metal oxide is referred to as an oxidesemiconductor in some cases. That is, an OS FET can also be called atransistor including a metal oxide or an oxide semiconductor.

Furthermore, in this specification and the like, a metal oxidecontaining nitrogen is also collectively referred to as a metal oxide insome cases. A metal oxide containing nitrogen may be referred to as ametal oxynitride.

Embodiment 1

In this embodiment, structures of an authentication system of oneembodiment of the present invention will be described with reference toFIG. 1, FIG. 2, and FIG. 11 to FIG. 13.

FIG. 1 shows diagrams illustrating a structure of the authenticationsystem of one embodiment of the present invention. FIG. 1A is a blockdiagram of the authentication system of one embodiment of the presentinvention. FIG. 1B is a top view of a reading portion used in theauthentication system of one embodiment of the present invention, andFIG. 1C is a cross-sectional view taken along a cutting line A1-A2 inFIG. 1B. FIG. 1D and FIG. 1E are schematic views each illustrating asituation where a palm image is captured using the reading portion ofthe authentication system of one embodiment of the present invention.

FIG. 2 is a flow chart showing a method for recording an unlockinghistory using the authentication system of one embodiment of the presentinvention.

FIG. 11 is a cross-sectional view illustrating a structure of a pixel ofa semiconductor device that can be used for the authentication system ofone embodiment of the present invention.

FIG. 12 is a circuit diagram illustrating a configuration of the pixelof the semiconductor device that can be used for the authenticationsystem of one embodiment of the present invention.

FIG. 13 shows block diagrams each illustrating a configuration of asemiconductor device that can be used for the authentication system ofone embodiment of the present invention.

Note that in this specification, an integer variable of 1 or more issometimes used in reference numerals. For example, (p) where p is aninteger variable of 1 or more is sometimes used in part of a referencenumeral that specifies any of p components at a maximum. For anotherexample, (m,n) where m and n are each an integer variable of 1 or moreis sometimes used in part of a reference numeral that specifies any ofm×n components at a maximum.

<Structure Example 1 of Authentication System>

The authentication system described in this embodiment includes anarithmetic device 610 and an input/output device 620 (see FIG. 1A).

<<Arithmetic Device 610>>

The arithmetic device 610 supplies control data CI1 and control dataCI2. The arithmetic device 610 is supplied with a sensor signal DS.

<<Input/output device 620>>

The input/output device 620 includes an electric lock 670 and a readingportion 660.

<<Electric Lock 670>>

The electric lock 670 is unlocked on the basis of the control data Cl2.

<<Reading Portion 660>>>

The reading portion 660 is supplied with the first control data CI1 andsupplies the sensor signal DS. In addition, the reading portion 660includes light-emitting elements 40 and a pixel array 151 (see FIG. 1B).

Any of the semiconductor devices described in Embodiment 2 can be usedfor the reading portion 660, for example.

<<Light-Emitting Element 40>>

The light-emitting element 40 emits light IR including infrared rays(see FIG. 1C).

<<Pixel Array 151>>

The pixel array 151 includes pixels 10 (see FIG. 13A).

<<Pixel 10>>

The pixels 10 each include an imaging circuit 100 and a photoelectricconversion element 12 (see FIG. 12).

The imaging circuit 100 is electrically connected to the photoelectricconversion element 12, and the imaging circuit 100 includes atransistor.

The transistor includes an oxide semiconductor film (see FIG. 11).

An oxide semiconductor film with a low carrier concentration ispreferably used for a transistor of one embodiment of the presentinvention. In the case where the carrier concentration of an oxidesemiconductor film is lowered, the impurity concentration in the oxidesemiconductor film is lowered to decrease the density of defect states.In this specification and the like, a state with a low impurityconcentration and a low density of defect states is referred to as ahighly purified intrinsic or substantially highly purified intrinsicstate. Examples of the impurities in an oxide semiconductor film includehydrogen, nitrogen, alkali metal, alkaline earth metal, iron, nickel,and silicon.

In particular, hydrogen contained in the oxide semiconductor film reactswith oxygen bonded to a metal atom to be water, and thus sometimes formsan oxygen vacancy in the oxide semiconductor film. If the channelformation region in the oxide semiconductor film includes oxygenvacancies, the transistor sometimes has normally-on characteristics. Insome cases, a defect that is an oxygen vacancy into which hydrogen hasentered functions as a donor and generates an electron serving as acarrier. In other cases, bonding of part of hydrogen to oxygen bonded toa metal atom generates an electron serving as a carrier. Thus, atransistor including an oxide semiconductor film which contains a largeamount of hydrogen is likely to be normally on.

A defect that is an oxygen vacancy into which hydrogen has entered canfunction as a donor of the oxide semiconductor film. However, it isdifficult to evaluate the defects quantitatively. Thus, the oxidesemiconductor film is sometimes evaluated by not its donor concentrationbut its carrier concentration. Therefore, in this specification and thelike, the carrier concentration assuming the state where an electricfield is not applied is sometimes used, instead of the donorconcentration, as the parameter of the oxide semiconductor film. Thatis, “carrier concentration” in this specification and the like may bereplaced with “donor concentration”.

Thus, in the case where an oxide semiconductor film is used for thetransistor, hydrogen in the oxide semiconductor film is preferablyreduced as much as possible. Specifically, the hydrogen concentration ofthe oxide semiconductor film, which is measured by secondary ion massspectrometry (SIMS), is lower than 1×10²⁰ atoms/cm³, preferably lowerthan 1×10¹⁹ atoms/cm³, more preferably lower than 5×10¹⁸ atoms/cm³,still more preferably lower than 1×10¹⁸ atoms/cm³. When an oxidesemiconductor film with sufficiently reduced impurities such as hydrogenis used for a channel formation region of a transistor, stableelectrical characteristics can be given.

The carrier concentration of an oxide semiconductor film functioning asa channel formation region is preferably lower than or equal to 1×10¹⁸cm⁻³, further preferably lower than 1×10¹⁷ cm⁻³, still furtherpreferably lower than 1×10¹⁶ cm⁻³, yet further preferably lower than1×10¹³ cm⁻³, and yet still further preferably lower than 1×10¹² cm⁻³.The minimum carrier density of an oxide semiconductor film at a channelformation region is not limited and can be 1×10⁻⁹ cm⁻³, for example.

<<Photoelectric Conversion Element 12>>

The photoelectric conversion element 12 includes an organicsemiconductor film (see FIG. 11).

Thus, an image of a physical feature can be taken, for example.Alternatively, an image of a vein spread or a vein arrangement patterncan be taken, for example. Alternatively, data included in a physicalfeature can be extracted. Alternatively, the security level can beincreased. As a result, a novel authentication system that is highlyconvenient or reliable can be provided.

<<Structure Example 2 of Arithmetic Device 610>>

The arithmetic device 610 also includes an arithmetic portion 611 and amemory portion 612 (see FIG. 1A).

The memory portion 612 stores a program and a database DB1.

The arithmetic portion 611 extracts a feature value from the sensorsignal DS on the basis of the program, and the arithmetic portion 611examines the feature value using the database DB1. In addition, thearithmetic portion 611 supplies the control data Cl2 on the basis of theexamination result.

In this manner, an individual having a predetermined physical featurecan be authenticated, for example. Alternatively, the security level canbe increased. As a result, a novel authentication system that is highlyconvenient or reliable can be provided.

<<Structure Example 2 of Memory Portion 612>>

The memory portion 612 also stores a database DB2.

The arithmetic portion 611 records the unlocking history in the databaseDB2 on the basis of the examination result.

Accordingly, the unlocking history can be recorded. Furthermore, theunlocking history can be recorded in association with an individualhaving a predetermined physical feature. Alternatively, the securitylevel can be increased. As a result, a novel authentication system thatis highly convenient or reliable can be provided.

<<Program>>

A program of one embodiment of the present invention includes a firststep to a seventh step (see FIG. 2).

[First Step]

In the first step, imaging is performed to obtain a sensor signal DS(see (S1) in FIG. 2). Specifically, the arithmetic device 610 of theauthentication system supplies the control signal CI1 (see FIG. 1A).Then, the light-emitting element 40 of the reading portion 660 emits thelight IR including infrared rays on the basis of the control signal CI1,and imaging is performed using the pixel array 151. Note that thereading portion 660 supplies the sensor signal DS. Thus, the arithmeticdevice 610 can obtain the sensor signal DS.

[Second Step]

In the second step, the program proceeds to the third step in the casewhere a change exceeding a predetermined level is observed in the sensorsignal DS, and the program proceeds to the first step in the case whereonly a change less than or equal to the predetermined level is observed(see (S2) in FIG. 2). For example, when an object that partly blocks orreflects the light IR is proximate to the reading portion 660, thesensor signal DS changes (see FIG. 1D or FIG. 1E). Thus, theauthentication system can recognize that a subject is near the readingportion 660.

[Third Step]

In the third step, imaging is performed to obtain a sensor signal DS(see (S3) in FIG. 2). Specifically, the arithmetic device 610 of theauthentication system supplies the control signal CI1 (see FIG. 1A). Thelight-emitting element 40 of the reading portion 660 emits the light IRincluding infrared rays on the basis of the control signal CI1, andimaging is performed using the pixel array 151. Note that the readingportion 660 supplies the sensor signal DS. Thus, the arithmetic device610 can obtain the sensor signal DS.

[Fourth Step]

In the fourth step, a feature value is extracted from the sensor signalDS (see (S4) in FIG. 2). For example, a feature value derived from avein spread or a vein arrangement pattern is extracted from the sensorsignal DS.

[Fifth Step]

In the fifth step, the feature value is examined using the database DB1,and the program proceeds to the sixth step in the case where thedatabase DB1 includes data matching the feature value. In the case wherethe database DB1 includes no data matching the feature value, theprogram proceeds to the first step (see (S5) in FIG. 2).

[Sixth Step]

In the sixth step, the control data CI2 is supplied to unlock theelectric lock 670 (see (S6) in FIG. 2).

[Seventh Step]

In the seventh step, the unlocking history is recorded in the databaseDB2 (see (S7) in FIG. 2).

Thus, the unlocking history can be recorded in the second database DB2.Furthermore, the unlocking history can be recorded in association withan individual having a predetermined physical feature. Alternatively,the security level can be increased. As a result, a novel method forrecording unlocking history, which is highly convenient or reliable, canbe provided.

Note that this embodiment can be combined with any of the otherembodiments in this specification as appropriate.

Embodiment 2

In this embodiment, a semiconductor device that can be used for theauthentication system of one embodiment of the present invention and afabrication method thereof will be described with reference to drawings.

First, a photoelectric conversion element is formed over a substrate,and an opening portion is also provided in the substrate. Next, aconductive layer is formed to be embedded in the opening portion. Then,a transistor is formed over the substrate. For example, a firsttransistor in which one of a source and a drain is electricallyconnected to one electrode of the photoelectric conversion element and asecond transistor in which one of a source and a drain is electricallyconnected to the conductive layer are formed.

Next, the back surface of the substrate over which the transistors areformed is polished to expose the conductive layer. After that, alight-emitting element including a pixel electrode, a light-emittinglayer, and a common electrode is formed so that the conductive layer andthe pixel electrode are electrically connected to each other. The aboveis the fabrication method of the semiconductor device that can be usedfor the authentication system of one embodiment of the presentinvention.

In the semiconductor device that can be used for the authenticationsystem of one embodiment of the present invention, light emitted fromthe light-emitting element and reflected by a subject is detected by thephotoelectric conversion element. The semiconductor device that can beused for the authentication system of one embodiment of the presentinvention can have a function of performing biometric authenticationsuch as fingerprint authentication or vein authentication by using, forexample, an element emitting infrared light as the light-emittingelement. Alternatively, the semiconductor device can have a function ofperforming failure analysis on an industrial product, for example.

Furthermore, the semiconductor device that can be used for theauthentication system of one embodiment of the present invention canhave a function of displaying an image by using an element emittingvisible light as the light-emitting element. Thus, with the use of anelement emitting both infrared light and visible light as thelight-emitting element, an image can be displayed while the biometricauthentication, the failure analysis, or the like is performed. Forexample, an authentication result can be displayed. Note that even inthe case where an element emitting visible light is used as thelight-emitting element, the biometric authentication, the failureanalysis, or the like can be performed by detecting the visible light,which is emitted from the light-emitting element and reflected by asubject, using the photoelectric conversion element.

In this specification and the like, infrared light refers to light witha wavelength greater than or equal to 0.7 μm and less than or equal to1000 μm, for example. In addition, near-infrared light that is lightwith a wavelength of greater than or equal to 0.7 μm and less than orequal to 2.5 μm might be simply referred to as infrared light, forexample.

In the semiconductor device that can be used for the authenticationsystem of one embodiment of the present invention, the light-emittingelement and the photoelectric conversion element are formed over a layerwhere transistors, wirings electrically connected to the transistors,and the like are formed. Accordingly, light emitted from thelight-emitting element can be inhibited from being blocked by thewirings and the like, so that the semiconductor device that can be usedfor the authentication system of one embodiment of the present inventioncan emit high-luminance light and the semiconductor device that can beused for the authentication system of one embodiment of the presentinvention can have reduced power consumption. Furthermore, lightincident on the semiconductor device can be inhibited from being blockedby the wirings and the like, so that the semiconductor device that canbe used for the authentication system of one embodiment of the presentinvention can have higher light detection sensitivity.

<Cross-Sectional Structure Example 1 of Pixel>

FIG. 3 is a cross-sectional view illustrating a structure example of thepixel 10, which is a pixel included in the semiconductor device of oneembodiment of the present invention. The pixel 10 includes a transistor101, a transistor 132, the photoelectric conversion element 12, thelight-emitting element 40, and the like between a substrate 30 and asubstrate 50. Here, transistors using a metal oxide in their channelformation regions (hereinafter, OS transistors) can be used as thetransistor 101 and the transistor 132, for example.

As illustrated in FIG. 3, the pixel 10 can have a stacked-layerstructure of a layer 61, a layer 62, and a layer 63. In the layer 61,the substrate 30, an insulating layer 81, an insulating layer 82, thetransistor 101, the transistor 132, an insulating layer 80, and aninsulating layer 86 are provided. The transistor 101 and the transistor132 are provided between the insulating layer 82 and the insulatinglayer 80. An insulating layer 84 and an insulating layer 85 are providedto cover channel formation regions, source regions, and drain regions ofthe transistor 101 and the transistor 132. An insulating layer 83 isprovided between the insulating layer 82 and the insulating layer 84.

A conductive layer 21 is provided to be electrically connected to one ofthe source and the drain of the transistor 101, and a conductive layer22 is provided to be electrically connected to the other of the sourceand the drain of the transistor 101. A conductive layer 23 is providedto be electrically connected to one of the source and the drain of thetransistor 132, and a conductive layer 24 is provided to be electricallyconnected to the other of the source and the drain of the transistor132. Note that the conductive layer 21 to the conductive layer 24 mayeach be referred to as a wiring. Similarly, other conductive layersprovided in the semiconductor device of one embodiment of the presentinvention may each be referred to as a wiring.

As the substrate 30, a silicon substrate, a glass substrate, a ceramicssubstrate, a resin substrate, or the like can be used. Note that asubstrate containing a material similar to that for the substrate 30 canbe used as other substrates provided in the semiconductor device of oneembodiment of the present invention.

It is preferable that at least one of the insulating layer 80 to theinsulating layer 86 be formed using a material through which impuritiessuch as water and hydrogen are less likely to diffuse. This enables theinsulating layers to function as barrier films, so that entry ofimpurities into the transistor 101, the transistor 132, and the like canbe inhibited efficiently. Consequently, the reliability of thesemiconductor device of one embodiment of the present invention can beincreased.

As the transistors provided in the layer 61, such as the transistor 101and the transistor 132, thin-film transistors such as OS transistors arepreferably used. In this case, elements such as the transistors providedin the layer 61 can be isolated from each other without provision of anelement isolation layer such as a field oxide film. Thus, thesemiconductor device of one embodiment of the present invention can befabricated by a simple method.

In the layer 62, a substrate 11 and the photoelectric conversion element12 are provided. The substrate 11 can be a silicon substrate, forexample. The silicon substrate can include a single crystal with acrystal orientation of (100), for example. The thickness of thesubstrate 11 is preferably greater than or equal to 2 μm and less thanor equal to 20 μm.

In this specification and the like, the surface of the substrate 11 onthe layer 61 side refers to a front surface, and the surface on thelayer 63 side refers to a back surface.

The photoelectric conversion element 12 can be provided over thesubstrate 11, and can be a pn-junction photodiode or a pin-junctionphotodiode, for example. The photoelectric conversion element 12 can beformed by, for example, provision of a low-resistance region 13 in thesubstrate 11. In the case where the substrate 11 is a p-type substrate,for example, the low-resistance region 13 is made to be an n-typeregion, whereby a pn-junction photodiode can be formed as thephotoelectric conversion element 12. Here, the electric resistance ofthe substrate 11 is preferably higher than or equal to 8 Ω·cm and lowerthan or equal to 12 Ω·cm.

In the case where the photoelectric conversion element 12 is formed byprovision of the low-resistance region 13 in the substrate 11, oneelectrode of the photoelectric conversion element 12 can include thelow-resistance region 13 and the other electrode of the photoelectricconversion element 12 can include the substrate 11. In the case wherethe substrate 11 is a p-type substrate and the low-resistance region 13is an n-type region, for example, an anode of the photoelectricconversion element 12 can include the substrate 11 and a cathode of thephotoelectric conversion element 12 can include the low-resistanceregion 13.

The low-resistance region 13 is electrically connected to the conductivelayer 21. Thus, one electrode of the photoelectric conversion element 12is electrically connected to one of the source and the drain of thetransistor 101 through the conductive layer 21. Therefore, thetransistor 101 can have a function of controlling the operation of thephotoelectric conversion element 12.

An opening portion is provided in the substrate 11 and an insulatinglayer 87 is provided to cover a side surface of the opening portion. Aconductive layer 14 is provided in the opening portion whose sidesurface is covered with the insulating layer 87, and the conductivelayer 14 is electrically connected to the conductive layer 23.

In the case where an OS transistor is used as the transistors providedin the layer 61, such as the transistor 101 and the transistor 132,hydrogen in the insulating layer provided in the vicinity of the channelformation region of the transistor is a factor of generating carriers ina metal oxide layer. For this reason, hydrogen in the insulating layerprovided in the vicinity of the channel formation region of the OStransistor is preferably as little as possible. Meanwhile, in the casewhere a silicon substrate is used as the substrate 11, hydrogen in theinsulating layer provided in the vicinity of the photoelectricconversion element 12 terminates a dangling bond of silicon. Thus,hydrogen in the insulating layer provided in the vicinity of thephotoelectric conversion element 12 is preferably as much as possible.When the insulating layer 80 is formed using a material that is lesslikely to transmit hydrogen, hydrogen can be confined to the substrate11 side and thus entry of hydrogen into the transistor 101, thetransistor 132, and the like can be inhibited. Thus, the reliability ofthe semiconductor device of one embodiment of the present invention canbe high compared to the case where the insulating layer 80 is notprovided.

Examples of the material that is less likely to transmit hydrogen andcan be used for the insulating layer 80 include aluminum oxide, aluminumoxynitride, gallium oxide, gallium oxynitride, yttrium oxide, yttriumoxynitride, hafnium oxide, hafnium oxynitride, and yttria-stabilizedzirconia (YSZ).

In the layer 63, a conductive layer 31, an insulating layer 32, thelight-emitting element 40, and an insulating layer 33 are provided. Thesubstrate 50 and a filter 51 are also provided in the layer 63. Thesubstrate 50 and the substrate 11 are sealed with a sealing layer 52. Anelement having a function of emitting white light and infrared light ispreferably used as the light-emitting element 40, for example.

The conductive layer 31 is provided to include a region in contact withthe substrate 11. Providing the conductive layer 31 can reduce theresistance of the other electrode of the photoelectric conversionelement 12.

The insulating layer 32 is provided to cover the conductive layer 31,and the light-emitting element 40 is provided over the insulating layer32. The light-emitting element 40 has a stacked-layer structure in whicha conductive layer 41, an EL layer 42, and a conductive layer 43 arestacked in this order from the insulating layer 32 side. That is, thelight-emitting element 40 can be an EL (Electro-Luminescence) element.Using an EL element as the light-emitting element 40 enables thesemiconductor device of one embodiment of the present invention to bedownsized and thinned, leading to application to a variety of electronicdevices and an improvement in portability of the electronic devices.

The conductive layer 41 is electrically connected to the conductivelayer 14 through the opening provided in the insulating layer 32. Inaddition, the insulating layer 33 is provided to cover an end of theconductive layer 41.

For the insulating layer 32 and the insulating layer 33, an oxideinsulating film, a nitride insulating film, an oxynitride insulatingfilm, or a nitride oxide insulating film can be used, for example. Theinsulating layers can each be formed to be a single layer or a stackedlayer. Examples of the oxide insulating film include a silicon oxidefilm, an aluminum oxide film, a gallium oxide film, a germanium oxidefilm, an yttrium oxide film, a zirconium oxide film, a lanthanum oxidefilm, a neodymium oxide film, a hafnium oxide film, and a tantalum oxidefilm. Examples of the nitride insulating film include a silicon nitridefilm and an aluminum nitride film. Examples of the oxynitride insulatingfilm include a silicon oxynitride film. Examples of the nitride oxideinsulating film include a silicon nitride oxide film. Note that otherinsulating layers included in the semiconductor device of one embodimentof the present invention, such as the insulating layer 81 to theinsulating layer 87 and gate insulating layers of the transistor 101 andthe transistor 132, can be insulating layers containing any of the abovematerials in some cases.

In this specification and the like, “silicon oxynitride” is a materialthat contains more oxygen than nitrogen in its composition. Moreover, inthis specification and the like, “silicon nitride oxide” is a materialthat contains more nitrogen than oxygen in its composition.

For the conductive layer 41, a low-resistance conductive film of a metalor the like can be used. For example, the conductive layer 41 can beformed using one or more kinds of metals such as tungsten (W),molybdenum (Mo), zirconium (Zr), hafnium (Hf), vanadium (V), niobium(Nb), tantalum (Ta), chromium (Cr), cobalt (Co), nickel (Ni), titanium(Ti), platinum (Pt), aluminum (Al), copper (Cu), and silver (Ag); alloysthereof; and metal nitrides thereof. Note that other conductive layersincluded in the semiconductor device of one embodiment of the presentinvention, such as the conductive layer 21 to the conductive layer 24,the conductive layer 14, and the source electrodes, the drainelectrodes, and the gate electrodes of the transistor 101 and thetransistor 132, can be conductive layers containing any of the abovematerials in some cases.

The conductive layer 41 and the conductive layer 43 have functions ofthe electrodes of the light-emitting element 40. Thus, it can be saidthat one electrode of the light-emitting element 40 is electricallyconnected to one of the source and the drain of the transistor 132through the conductive layer 14 and the conductive layer 23. Therefore,the transistor 132 can have a function of controlling the operation ofthe light-emitting element 40. Note that the conductive layer 41 canhave a function of a pixel electrode of the light-emitting element 40,for example, and the conductive layer 43 can have a function of a commonelectrode of the light-emitting element 40, for example.

As the conductive layer 43, a conductive layer having alight-transmitting property can be used. For example, in the case wherethe light-emitting element 40 has a function of emitting visible lightand infrared light, a light-transmitting conductive layer that transmitsvisible light and infrared light can be used as the conductive layer 43.For example, an indium oxide containing tungsten oxide, an indium zincoxide containing tungsten oxide, an indium oxide containing titaniumoxide, an indium tin oxide (ITO), an indium tin oxide containingtitanium oxide, an indium zinc oxide, or an indium tin oxide to whichsilicon oxide is added can be used. Alternatively, a cadmium tin oxide(CTO) or the like can be used.

The sealing layer 52 has a function of inhibiting entry of oxygen,hydrogen, moisture, carbon dioxide, or the like into the light-emittingelement 40. As the sealing layer 52, an ultraviolet curable resin or athermosetting resin can be used as well as an inert gas such as nitrogenor argon; for example, PVC (polyvinyl chloride), an acrylic resin,polyimide, an epoxy resin, a silicone resin, PVB (polyvinyl butyral),EVA (ethylene vinyl acetate), or the like can be used. A drying agentmay be contained in the sealing layer 52.

As part of the sealing layer 52, a protective layer of, for example,silicon nitride, silicon nitride oxide, aluminum oxide, aluminumnitride, aluminum oxynitride, aluminum nitride oxide, or DLC (DiamondLike Carbon) may be provided.

The filter 51 is provided to include a region overlapping with thephotoelectric conversion element 12 and the light-emitting element 40,with the sealing layer 52 therebetween. The filter 51 has a function ofabsorbing light with a specific wavelength. For example, the filter 51has a function of absorbing light except red light. In this case, whenwhite light is emitted from the light-emitting element 40, red light isemitted to the outside of the pixel 10 through the substrate 50 and thelike. Alternatively, the filter 51 has a function of absorbing lightexcept green light, for example. In this case, when white light isemitted from the light-emitting element 40, green light is emitted tothe outside of the pixel 10 through the substrate 50 and the like.Alternatively, the filter 51 has a function of absorbing light exceptblue light, for example. In this case, when white light is emitted fromthe light-emitting element 40, blue light is emitted to the outside ofthe pixel 10 through the substrate 50 and the like.

Alternatively, the filter 51 can have a structure with a function ofabsorbing light except infrared light. For example, the filter 51 has afunction of absorbing visible light. In this case, when white light andinfrared light are emitted from the light-emitting element 40, infraredlight is emitted to the outside of the pixel 10 through the substrate 50and the like.

The pixel 10 includes the photoelectric conversion element 12 and thelight-emitting element 40. Thus, light emitted from the light-emittingelement 40 to the outside of the pixel 10 through the substrate 50 andthe like, hit a subject, and reflected thereby can be detected by thephotoelectric conversion element 12. Accordingly, using an elementemitting infrared light as the light-emitting element 40, for example,enables the semiconductor device of one embodiment of the presentinvention to have a function of detecting an object. For example, veinauthentication can be performed by holding a palm over the semiconductordevice of one embodiment of the present invention, and fingerprintauthentication can be performed by holding a finger thereover. That is,the semiconductor device of one embodiment of the present invention canhave a function of performing biometric authentication. In addition, thesemiconductor device of one embodiment of the present invention can beused for non-destructive inspection such as foreign substance inspectionof a food and failure analysis of an industrial product.

When the filter 51 is provided to include a region overlapping not onlywith the light-emitting element 40 but also with the photoelectricconversion element 12, light with a wavelength other than the wavelengthof light emitted from the light-emitting element 40 to the outside ofthe pixel 10 through the substrate 50 can be inhibited from beingincident on the photoelectric conversion element 12. This can increasethe detection accuracy of the photoelectric conversion element 12,leading to higher reliability of the semiconductor device of oneembodiment of the present invention.

When the light-emitting element 40 has a function of emitting visiblelight such as white light, the semiconductor device of one embodiment ofthe present invention can have a function of displaying an image. Forexample, an image corresponding to imaging data obtained by thephotoelectric conversion element 12 can be displayed using thelight-emitting element 40. Alternatively, information obtained from theimaging data obtained by the photoelectric conversion element 12, suchas an authentication result, can be displayed. Alternatively, an imagecorresponding to image data supplied from the outside of the pixel 10can be displayed. For example, an image corresponding to image dataobtained through the Internet can be displayed.

As described above, the semiconductor device of one embodiment of thepresent invention can display an image while performing the biometricauthentication, the failure analysis, or the like by using an elementemitting both infrared light and visible light as the light-emittingelement 40. Note that even in the case where an element emitting visiblelight is used as the light-emitting element 40, the biometricauthentication, the failure analysis, or the like can be performed bydetecting visible light, which is emitted from the light-emittingelement 40 to the outside of the pixel 10 through the substrate 50 andthe like and reflected by a subject, using the photoelectric conversionelement 12.

Thus, the semiconductor device of one embodiment of the presentinvention can be regarded as a semiconductor device including an imagingdevice provided with the photoelectric conversion element 12 and adisplay device provided with the light-emitting element 40.

Note that the substrate 50 is a substrate having a light-transmittingproperty, such as a glass substrate. Thus, light emitted from thelight-emitting element 40 and light incident on the photoelectricconversion element 12 can be inhibited from being blocked by thesubstrate 50. Accordingly, the semiconductor device of one embodiment ofthe present invention can emit high-luminance light and thesemiconductor of one embodiment of the present invention can havereduced power consumption. Furthermore, the semiconductor device of oneembodiment of the present invention can have higher light detectionsensitivity.

Like the conductive layer 43, the conductive layer 31 can be formedusing a conductive layer having a light-transmitting property. Forexample, a light-transmitting conductive layer that transmits visiblelight and infrared light can be used. In this case, light incident onthe photoelectric conversion element 12 can be inhibited from beingblocked by the conductive layer 31, leading to higher light detectionsensitivity of the semiconductor device of one embodiment of the presentinvention. Note that the conductive layer 31 can contain a material thatcan be used for the conductive layer 43, for example.

Note that the EL layer 42 overlapping with the conductive layer 41 andthe conductive layer 43 can emit light, whereas the EL layer 42overlapping with the conductive layer 43 but not overlapping with theconductive layer 41 cannot emit light. Since the EL layer 42 is anextremely thin film, absorption of visible light and infrared light canbe ignored. Accordingly, the EL layer 42 and the conductive layer 43 canbe provided to overlap with the photoelectric conversion element 12.

As illustrated in FIG. 3, in the pixel 10, the photoelectric conversionelement 12 and the light-emitting element 40 are formed over the layer61 where the transistors, the wirings electrically connected to thetransistors, and the like are formed. Accordingly, light emitted fromthe light-emitting element 40 can be inhibited from being blocked by thewirings and the like, so that the semiconductor device of one embodimentof the present invention can emit high-luminance light and thesemiconductor device of one embodiment of the present invention can havereduced power consumption. Furthermore, light incident on thesemiconductor device can be inhibited from being blocked by the wiringsand the like, so that the semiconductor device of one embodiment of thepresent invention can have higher light detection sensitivity.

FIG. 4A is a diagram illustrating a structure example of thesemiconductor device of one embodiment of the present invention. FIG. 4Aillustrates structure examples of a pixel 10R, a pixel 10G, a pixel 10B,and a pixel 10IR as the pixel 10.

The structure illustrated in FIG. 3 can be used for each of the pixel10R, the pixel 10G, the pixel 10B, and the pixel 10IR. Although thelayer 61 is omitted in FIG. 4A, the pixel 10R, the pixel 10G, the pixel10B, and the pixel 10IR each actually include the layer 61.

The semiconductor device of one embodiment of the present invention canhave a structure in which side surfaces of the photoelectric conversionelement 12 having the structure illustrated in FIG. 4A are surrounded bya light control layer 56. The light control layer 56 has a function ofan element isolation layer between adjacent photoelectric conversionelements 12. Light incident from the light-receiving surface toward theside surface of the photoelectric conversion element 12 can be reflectedor attenuated by the light control layer 56. Accordingly, the light canbe prevented from entering an adjacent photoelectric conversion element12. This can increase the detection accuracy of the photoelectricconversion element 12, leading to higher reliability of thesemiconductor device of one embodiment of the present invention. Notethat the light control layer 56 is not necessarily provided.

A material having a lower refractive index than silicon is preferablyused for the light control layer 56. For example, an insulator such asaluminum oxide, magnesium oxide, silicon oxide, silicon oxynitride,silicon nitride oxide, silicon nitride, gallium oxide, germanium oxide,yttrium oxide, zirconium oxide, lanthanum oxide, neodymium oxide,hafnium oxide, or tantalum oxide can be used. Alternatively, an organicmaterial such as an acrylic resin or polyimide may be used. The use of amaterial having a lower refractive index than silicon facilitates totalreflection of light incident on the side surface of the photoelectricconversion element 12. Furthermore, a gas such as air, nitrogen, oxygen,argon, or helium can be used instead of the above material. In thiscase, the gas may have a pressure lower than an atmospheric pressure.

A material that is likely to absorb light may be used for the lightcontrol layer 56. For example, it is possible to use a resin to which amaterial such as a carbon-based black pigment such as carbon black, atitanium-based black pigment such as titanium black, an oxide of iron, acomposite oxide of copper and chromium, or a composite oxide of copper,chromium, and zinc is added.

As described above, the light-emitting element 40 provided in the layer63 can have a function of emitting white light and infrared light, forexample. In the layer 63 included in the pixel 10R, a filter 51R can beprovided to include a region overlapping with the photoelectricconversion element 12 and the light-emitting element 40. The filter 51Rhas a function of transmitting red light, for example. Thus, the pixel10R can have functions of emitting red light and detecting red light bythe photoelectric conversion element 12.

In the layer 63 included in the pixel 10G, a filter 51G can be providedto include a region overlapping with the photoelectric conversionelement 12 and the light-emitting element 40. The filter 51G has afunction of transmitting green light, for example. Thus, the pixel 10Gcan have functions of emitting green light and detecting green light bythe photoelectric conversion element 12.

In the layer 63 included in the pixel 10B, a filter 51B can be providedto include a region overlapping with the photoelectric conversionelement 12 and the light-emitting element 40. The filter 51B has afunction of transmitting blue light, for example. Thus, the pixel 10Bcan have functions of emitting blue light and detecting blue light bythe photoelectric conversion element 12.

In the layer 63 included in the pixel 10IR, a filter 51IR can beprovided to include a region overlapping with the photoelectricconversion element 12 and the light-emitting element 40. The filter 51IRhas functions of transmitting infrared light and absorbing visiblelight, for example. Thus, the pixel 10B can have functions of emittinginfrared light and detecting infrared light by the photoelectricconversion element 12.

The pixel 10R has functions of emitting red light and detecting thelight, the pixel 10G has functions of emitting green light and detectingthe light, the pixel 10B has functions of emitting blue light anddetecting the light, and the pixel 10IR has functions of emittinginfrared light and detecting the light; thus, the semiconductor deviceof one embodiment of the present invention can have functions ofdisplaying a color image and detecting visible light and infrared light.Note that the pixel 10R, the pixel 10G, and the pixel 10B may each havefunctions of emitting light of yellow, cyan, magenta, or the like anddetecting the light.

Here, the pixel 10R, the pixel 10G, the pixel 10B, and the pixel 10IRcan each be referred to as a subpixel. In addition, the pixel 10R, thepixel 10G, the pixel 10B, and the pixel 10IR can be regarded as formingone pixel. Note that in this specification and the like, the term“pixel” refers to “subpixel” in some cases. For example, the pixel 10can be referred to as a subpixel.

In the pixel 10R, a filter 53 can be provided to include a regionoverlapping with the filter 51R. In the pixel 10G, the filter 53 can beprovided to include a region overlapping with the filter 51G. In thepixel 10B, the filter 53 can be provided to include a region overlappingwith the filter 51B. The filter 53 has functions of transmitting visiblelight and absorbing infrared light, for example. That is, the filter 53can be regarded as an infrared light cut filter.

Providing the filter 53 in the pixel 10R, the pixel 10G, and the pixel10B inhibits infrared light from being detected by the photoelectricconversion element 12 included in the pixel 10R, the photoelectricconversion element 12 included in the pixel 10G, and the photoelectricconversion element 12 included in the pixel 10B, even in the case whereall the light-emitting elements 40 have a function of emitting infraredlight, for example. This can increase the detection accuracy of thephotoelectric conversion element 12, leading to higher reliability ofthe semiconductor device of one embodiment of the present invention.

Although FIG. 4A illustrates a structure in which the filter 53 isprovided over the filter 51R, the filter 51G, and the filter 51B, thefilter 53 may be provided below the filter 51R, the filter 51G, and thefilter 51B.

A microlens 54 can be provided over the layer 63 to include a regionoverlapping with the photoelectric conversion element 12. This canincrease the light detection sensitivity of the photoelectric conversionelement 12.

FIG. 4B is a diagram illustrating a structure example of thesemiconductor device of one embodiment of the present invention, and isa modification example of the structure illustrated in FIG. 4A. Thesemiconductor device having the structure illustrated in FIG. 4B isdifferent from the semiconductor device having the structure illustratedin FIG. 4A in that the filter 53 is not provided in the pixel 10G andthe pixel 10B.

The filter 51G and the filter 51B each have a function of absorbing redlight. Thus, infrared light with a wavelength close to that of red lightis also absorbed in some cases. In this case, infrared light can beinhibited from being detected by the photoelectric conversion element 12provided in the pixel 10G and the photoelectric conversion element 12provided in the pixel 10B, even when the pixel 10G and the pixel 10B arenot provided with the filter 53 having a function of absorbing infraredlight. When the semiconductor device of one embodiment of the presentinvention has the structure illustrated in FIG. 4B, light emitted fromthe light-emitting element 40 included in the pixel 10G and lightemitted from the light-emitting element 40 included in the pixel 10B canbe inhibited from being absorbed by the filter 53. Thus, thesemiconductor device of one embodiment of the present invention can emithigh-luminance light and the semiconductor device of one embodiment ofthe present invention can have reduced power consumption. Furthermore,the semiconductor device of one embodiment of the present invention canhave higher light detection sensitivity.

<Example of Fabrication Method of Pixel>

FIG. 5A, FIG. 5B, FIG. 5C, FIG. 5D, FIG. 6A, FIG. 6B, FIG. 6C, FIG. 7A,and FIG. 7B are diagrams illustrating an example of a fabrication methodof the pixel 10 having the structure illustrated in FIG. 3.

Note that thin films that form the light-emitting device (insulatingfilms, semiconductor films, conductive films, and the like) can beformed by a sputtering method, a chemical vapor deposition (CVD) method,a vacuum evaporation method, a pulsed laser deposition (PLD) method, anatomic layer deposition (ALD) method, or the like. Examples of the CVDmethod include a plasma-enhanced chemical vapor deposition (PECVD)method and a thermal CVD method. In addition, examples of the thermalCVD method include a metal organic chemical vapor deposition (MOCVD)method.

Alternatively, the thin films that form the light-emitting device (theinsulating films, the semiconductor films, the conductive films, and thelike) can be formed by a method such as spin coating, dipping, spraycoating, or a droplet discharging method (e.g., ink jetting anddispensing), a printing method (e.g., screen printing and offsetprinting), or with an equipment such as a doctor knife, a slit coater, aroll coater, a curtain coater, or a knife coater.

When the thin films that form the light-emitting device are processed, aphotolithography method or the like can be used for the processing.Alternatively, the thin films may be processed by a nanoimprintingmethod, a sandblasting method, a lift-off method, or the like.Island-shaped thin films may be directly formed by a film formationmethod using a blocking mask such as a metal mask.

There are two typical examples of a photolithography method. In one ofthe methods, a resist mask is formed over a thin film that is to beprocessed, and the thin film is processed by etching or the like, sothat the resist mask is removed. In the other method, after aphotosensitive thin film is formed, exposure and development areperformed, so that the thin film is processed into a desired shape.

For light used for exposure in a photolithography method, for example,an i-line (with a wavelength of 365 nm), a g-line (with a wavelength of436 nm), an h-line (with a wavelength of 405 nm), or light in whichthese lines are mixed can be used. Besides, ultraviolet light, KrF laserlight, ArF laser light, or the like can be used. Furthermore, exposuremay be performed by liquid immersion light exposure technique.Furthermore, as the light used for the exposure, extreme ultra-violet(EUV) light or X-rays may be used. Furthermore, instead of the lightused for the exposure, an electron beam can also be used. It ispreferable to use extreme ultra-violet light, X-rays, or an electronbeam because extremely minute processing can be performed. Note thatwhen light exposure is performed by scanning of a beam such as anelectron beam, a photomask is unnecessary.

For etching of the thin films, a dry etching method, a wet etchingmethod, a sandblast method, or the like can be used.

The example of a fabrication method of the pixel 10 having the structureillustrated in FIG. 3 is described. First, the low-resistance region 13is formed in the substrate 11 (FIG. 5A). Accordingly, the photoelectricconversion element 12 can be fabricated. The low-resistance region 13can be formed by impurity addition to the substrate 11. For example,adding a pentavalent element such as phosphorus or arsenic can make thelow-resistance region 13 an n-type region, and adding a trivalentelement such as boron or aluminum can make the low-resistance region 13a p-type region. Note that the low-resistance region 13 can be an n-typeregion in the case where the substrate 11 is a p-type substrate, and thelow-resistance region 13 can be a p-type region in the case where thesubstrate 11 is an n-type substrate.

Example of the method for adding the above impurity include an ionimplantation method in which an ionized source gas is subjected to massseparation and then added, an ion doping method in which an ionizedsource gas is added without mass separation, and a plasma immersion ionimplantation method.

Next, an opening portion is provided in the substrate 11. The openingportion need not penetrate the substrate 11. Then, the insulating layer87 is provided to cover a side surface of the opening portion, and theconductive layer 14 is formed to fill the opening portion covered withthe insulating layer 87 (FIG. 5B).

An SOI substrate may be used as the substrate 11. In this case, anopening portion is provided in the substrate 11 to reach a BOX layer.

Next, the insulating layer 86 is formed over the insulating layer 87 andthe conductive layer 14, and the insulating layer 80 is formed over theinsulating layer 86. After that, the transistor 101 and the transistor132 are formed over the insulating layer 80. Note that the insulatinglayer 85 and the insulating layer 84 are formed to cover the channelformation regions, the source regions, and the drain regions of thetransistor 101 and the transistor 132. In addition, the insulating layer83 is formed over the insulating layer 84. The insulating layer 83 has afunction of an interlayer insulating film and is planarized byplanarization treatment using a chemical mechanical polishing (CMP)method or the like. Note that the insulating layer 83 is not necessarilyplanarized. In addition, the layers other than the insulating layer 83can be subjected to planarization treatment by a CMP method or the like.

The transistor 101 and the transistor 132 can be formed through the sameprocess. In other words, a transistor having a function of controllingthe operation of the photoelectric conversion element 12 and atransistor having a function of controlling the operation of thelight-emitting element 40 can be fabricated through the same process.Thus, the fabrication process of the semiconductor device of oneembodiment of the present invention can be simplified compared to thecase where the transistor having a function of controlling the operationof the photoelectric conversion element 12 and the transistor having afunction of controlling the operation of the light-emitting element 40are fabricated through different processes. Therefore, the semiconductordevice of one embodiment of the present invention can be inexpensive.Note that a circuit element other than the transistors, such as acapacitor, can be fabricated through the same process as thetransistors.

After formation of the transistor 101, the transistor 132, and the like,the insulating layer 82 is formed. Next, opening portions are providedin the insulating layer 80 and the insulating layer 82 to the insulatinglayer 87, and the conductive layer 21 to the conductive layer 24 areformed to fill the opening portions. Specifically, the conductive layer21 is formed to be electrically connected to the low-resistance region13 and one of the source and the drain of the transistor 101, and theconductive layer 22 is formed to be electrically connected to the otherof the source and the drain of the transistor 101. The conductive layer23 is formed to be electrically connected to the conductive layer 14 andone of the source and the drain of the transistor 132, and theconductive layer 24 is formed to be electrically connected to the otherof the source and the drain of the transistor 132.

After formation of the conductive layer 21 to the conductive layer 24,the insulating layer 81 is formed over the conductive layer 21 to theconductive layer 24 and the insulating layer 82 (FIG. 5C). After that,the substrate 30 is attached to the insulating layer 81 (FIG. 5D). Theinsulating layer 81 and the substrate 30 can be attached to each otherby compression bonding, for example. Alternatively, the substrate 30 canbe attached to the insulating layer 81 with an adhesive layer providedbetween the insulating layer 81 and the substrate 30. The substrate 30has a function of a support substrate in the subsequent fabricationsteps.

Next, the back surface of the substrate 11 and the insulating layer 87are polished to expose the conductive layer 14 (FIG. 6A). The substrate11 can be polished using a grinder, for example. After the substrate 11is polished using a grinder, the substrate 11 and the insulating layer87 are polished by a CMP method, whereby the conductive layer 14 can beexposed. The use of a grinder enables high-speed polishing of thesubstrate 11. Furthermore, the use of a CMP method enables precisepolishing of the substrate 11 and the insulating layer 87, and canincrease the planarity of the substrate 11. Note that a portionsurrounded by a dotted line in FIG. 6A is the polished portion of thesubstrate 11.

In the case where the substrate 11 is an SOI substrate, the conductivelayer 14 can be exposed by polishing a BOX layer, which is a layercontaining a material different from a material contained in thelow-resistance region 13. In this manner, the polishing step can becontrolled easily.

Next, the conductive layer 31 is formed over the substrate 11 (FIG. 6B).Specifically, a conductive film is formed over the substrate 11, theconductive layer 14, and the insulating layer 87, and then patterning isperformed by a photolithography method or the like. After that, aportion of the conductive film in contact with the conductive layer 14is removed by an etching method or the like. In the above manner, theconductive layer 31 can be formed. Note that the conductive layer 31does not include a region in contact with the insulating layer 87 inFIG. 6B, but may include a region in contact with the insulating layer87.

Next, the insulating layer 32 is formed to cover the conductive layer 31(FIG. 6C). Specifically, an insulating film is formed over theconductive layer 31, the substrate 11, the conductive layer 14, and theinsulating layer 87, and an opening portion reaching the conductivelayer 14 is formed in the insulating film, whereby the insulating layer32 can be formed. Note that the insulating layer 32 includes a region incontact with the insulating layer 87 in FIG. 6C, but does notnecessarily include a region in contact with the insulating layer 87. Inaddition, the insulating layer 32 does not include a region in contactwith the conductive layer 14 in FIG. 6C, but may include a region incontact with the conductive layer 14.

Next, the conductive layer 41 is formed to be electrically connected tothe conductive layer 14. After that, the EL layer 42 is formed toinclude a region overlapping with the conductive layer 41, and theconductive layer 43 is formed to include a region overlapping with theconductive layer 41 and the EL layer 42 (FIG. 7A). In the above manner,the light-emitting element 40 can be fabricated. Here, the EL layer 42can be formed by an evaporation method, a coating method, a printingmethod, a discharge method, or the like.

Next, the filter 51 is formed over the substrate 50 (FIG. 7B). Here, thefilter 53 having a function of an infrared light cut filter may beformed in addition to the filter 51. Note that the filter 51 and thefilter 53 can be formed by an evaporation method (including a vacuumevaporation method), a transfer method, a printing method, an inkjetmethod, a coating method, or the like.

After that, the substrate 50 and the substrate 11 are sealed with thesealing layer 52. The above is the example of the fabrication method ofthe pixel 10 having the structure illustrated in FIG. 3.

When the pixel 10 is fabricated by the method illustrated in FIG. 5 toFIG. 7, the photoelectric conversion element 12 and the light-emittingelement 40 can be formed over the layer 61, which is a layer where thetransistors, the wirings electrically connected to the transistors, andthe like are formed. Accordingly, light emitted from the light-emittingelement 40 can be inhibited from being blocked by the wirings and thelike, so that high-luminance light can be emitted from the semiconductordevice of one embodiment of the present invention, and the powerconsumption of the semiconductor device of one embodiment of the presentinvention can be reduced. Furthermore, light incident on thesemiconductor device can be inhibited from being blocked by the wiringsand the like, so that the semiconductor device of one embodiment of thepresent invention can have higher light detection sensitivity.

<Structure Example of Light-Emitting Element>

FIG. 8A to FIG. 8C are diagrams illustrating structure examples of thelight-emitting element 40. FIG. 8A illustrates a structure (a singlestructure) in which the EL layer 42 is sandwiched between the conductivelayer 41 and the conductive layer 43. As described above, the EL layer42 contains a light-emitting material, for example, a light-emittingmaterial of an organic compound.

FIG. 8B is a diagram illustrating a stacked-layer structure of the ELlayer 42. In the light-emitting element 40 having the structureillustrated in FIG. 8B, the conductive layer 41 has a function of ananode and the conductive layer 43 has a function of a cathode.

The EL layer 42 has a structure in which a hole-injection layer 71, ahole-transport layer 72, a light-emitting layer 73, anelectron-transport layer 74, and an electron-injection layer 75 arestacked in this order over the conductive layer 41. Note that in thecase where the conductive layer 41 has a function of the cathode and theconductive layer 43 has a function of the anode, the stacking order isreversed.

The light-emitting layer 73 contains a light-emitting material and aplurality of materials in appropriate combination, so that fluorescenceor phosphorescence of a desired emission color can be obtained. Thelight-emitting layer 73 may have a stacked-layer structure havingdifferent emission colors. In this case, different materials may be usedfor the light-emitting substance and other substances used in each ofthe light-emitting layers that are stacked.

For example, when the light-emitting element 40 has a micro opticalresonator (microcavity) structure with the conductive layer 41 and theconductive layer 43 illustrated in FIG. 8B respectively serving as areflective electrode and a semi-transmissive and semi-reflectiveelectrode, light obtained from the light-emitting layer 73 included inthe EL layer 42 can be resonated between the electrodes and thus thelight emitted through the conductive layer 43 can be intensified.

Note that in the case where the conductive layer 41 of thelight-emitting element 40 is a reflective electrode having astacked-layer structure of a reflective conductive material and alight-transmitting conductive material (transparent conductive film),optical adjustment can be performed by adjusting the thickness of thetransparent conductive film. Specifically, when the wavelength of lightobtained from the light-emitting layer 73 is λ, the distance between theconductive layer 41 and the conductive layer 43 is preferably adjustedto around mλ/2 (note that m is a natural number).

To amplify desired light (wavelength: λ) obtained from thelight-emitting layer 73, the optical path length from the conductivelayer 41 to a region of the light-emitting layer where desired light isobtained (light-emitting region) and the optical path length from theconductive layer 43 to the region of the light-emitting layer 73 wheredesired light is obtained (light-emitting region) are preferablyadjusted to around (2m′+1) λ/4 (note that m′ is a natural number). Here,the light-emitting region means a region where holes and electrons arerecombined in the light-emitting layer 73.

By such optical adjustment, the spectrum of specific monochromatic lightobtained from the light-emitting layer 73 can be narrowed and lightemission with high color purity can be obtained.

In the above case, the optical path length between the conductive layer41 and the conductive layer 43 is, to be exact, the total thickness froma reflective region in the conductive layer 41 to a reflective region inthe conductive layer 43. However, it is difficult to precisely determinethe reflective region in the conductive layer 41 and the conductivelayer 43; hence, it is assumed that the above effect is sufficientlyobtained with given positions in the conductive layer 41 and theconductive layer 43 being supposed to be reflective regions.Furthermore, the optical path length between the conductive layer 41 andthe light-emitting layer where desired light is obtained is, to beexact, the optical path length between the reflective region in theconductive layer 41 and the light-emitting region where desired light isobtained in the light-emitting layer. However, it is difficult toprecisely determine the reflective region in the conductive layer 41 andthe light-emitting region in the light-emitting layer where the desiredlight is obtained; thus, it is assumed that the above effect can besufficiently obtained with a given position in the conductive layer 41being supposed to be the reflective region and a given position in thelight-emitting layer where the desired light is obtained being supposedto be the light-emitting region.

The light-emitting element 40 illustrated in FIG. 8B has a microcavitystructure, so that light (monochromatic light) with differentwavelengths can be extracted even if the same EL layer is used. Thus,separate coloring for obtaining different emission colors is notnecessary. Therefore, high definition can be easily achieved. Inaddition, a combination with coloring layers is also possible.Furthermore, the emission intensity of light with a specific wavelengthin the front direction can be increased, whereby power consumption canbe reduced.

Note that the light-emitting element 40 illustrated in FIG. 8B does notnecessarily have a microcavity structure. In this case, light ofpredetermined colors can be extracted when the light-emitting layer 73has a structure for emitting white light and infrared light and coloringlayers are provided. When the EL layers 42 are formed by separatecoloring for obtaining different emission colors, light of predeterminedcolors can be extracted without providing coloring layers.

At least one of the conductive layer 41 and the conductive layer 43 canbe a light-transmitting electrode (e.g., a transparent electrode or asemi-transmissive and semi-reflective electrode). In the case where thelight-transmitting electrode is a transparent electrode, the visiblelight transmittance of the transparent electrode is higher than or equalto 40%. In the case where the light-transmitting electrode is asemi-transmissive and semi-reflective electrode, the visible lightreflectance of the semi-transmissive and semi-reflective electrode ishigher than or equal to 20% and lower than or equal to 80%, preferablyhigher than or equal to 40% and lower than or equal to 70%. Theseelectrodes preferably have a resistivity less than or equal to 1×10⁻²Ωcm.

In the case where the conductive layer 41 or the conductive layer 43 isan electrode having reflectivity (reflective electrode), the visiblelight reflectance of the electrode having reflectivity is higher than orequal to 40% and lower than or equal to 100%, preferably higher than orequal to 70% and lower than or equal to 100%. This electrode preferablyhas a resistivity less than or equal to 1×10⁻² Ωcm.

The structure of the light-emitting element 40 may be the structureillustrated in FIG. 8C. FIG. 8C illustrates a structure (a tandemstructure) of the light-emitting element 40 in which three EL layers (anEL layer 42 a, an EL layer 42 b, and an EL layer 42 c) are providedbetween the conductive layer 41 and the conductive layer 43. Here, acharge generation layer 44 a is provided between the EL layer 42 a andthe EL layer 42 b, and a charge generation layer 44 b is providedbetween the EL layer 42 b and the EL layer 42 c.

The EL layer 42 a has a function of emitting blue light, the EL layer 42b has a function of emitting yellow light, and the EL layer 42 c has afunction of emitting infrared light, for example. Since thecomplementary color of blue is yellow, the light-emitting element 40having the structure illustrated in FIG. 8C can have a function ofemitting white light and infrared light.

When the light-emitting element 40 has the tandem structure, the currentefficiency and the external quantum efficiency of the light-emittingelement 40 can be increased. Accordingly, the light-emitting element 40can emit high-luminance light. Furthermore, the semiconductor device ofone embodiment of the present invention can have reduced powerconsumption. Here, the EL layer 42 a, the EL layer 42 b, and the ELlayer 42 c can have a structure similar to that of the EL layer 42illustrated in FIG. 8B.

The charge generation layer 44 a has a function of injecting electronsinto one of the EL layer 42 a and the EL layer 42 b and injecting holesinto the other when a voltage is supplied between the conductive layer41 and the conductive layer 43. The charge generation layer 44 b has afunction of injecting electrons into one of the EL layer 42 b and the ELlayer 42 c and injecting holes into the other when a voltage is suppliedbetween the conductive layer 41 and the conductive layer 43. Thus, whena voltage is supplied so that the potential of the conductive layer 41is higher than the potential of the conductive layer 43, electrons areinjected from the charge generation layer 44 a into the EL layer 42 a,and holes are injected from the charge generation layer 44 a into the ELlayer 42 b. In addition, electrons are injected from the chargegeneration layer 44 b into the EL layer 42 b, and holes are injectedfrom the charge generation layer 44 b into the EL layer 42 c.

Note that in terms of light extraction efficiency, the charge generationlayer 44 preferably transmits visible light (specifically, the visiblelight transmittance of the charge generation layer 44 is preferably 40%or higher). The conductivity of the charge generation layer 44 may belower than the conductivity of the conductive layer 41 or theconductivity of the conductive layer 43.

<Materials for Light-Emitting Element>

Next, materials that can be used for the light-emitting element 40 aredescribed.

<<Conductive Layer 41 and Conductive Layer 43>>

For the conductive layer 41 and the conductive layer 43, materials givenbelow can be used in appropriate combination as long as the functions ofthe anode and the cathode can be fulfilled. For example, a metal, analloy, an electrically conductive compound, a mixture of these, and thelike can be appropriately used. Specifically, an In—Sn oxide (alsoreferred to as ITO), an In—Si—Sn oxide (also referred to as ITSO), anIn—Zn oxide, or an In—W—Zn oxide can be used. In addition, it ispossible to use a metal such as aluminum (Al), titanium (Ti), chromium(Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu),gallium (Ga), zinc (Zn), indium (In), tin (Sn), molybdenum (Mo),tantalum (Ta), tungsten (W), palladium (Pd), gold (Au), platinum (Pt),silver (Ag), yttrium (Y), or neodymium (Nd) or an alloy containing anappropriate combination of any of these metals. It is also possible touse an element belonging to Group 1 or Group 2 of the periodic table,which is not described above (e.g., lithium (Li), cesium (Cs), calcium(Ca), or strontium (Sr)), a rare earth metal such as europium (Eu) orytterbium (Yb), an alloy containing an appropriate combination of any ofthese elements, graphene, or the like.

<<Hole-Injection Layer 71 and Hole-Transport Layer 72>>

The hole-injection layer 71 is a layer injecting holes from theconductive layer 41 that is the anode or the charge generation layer 44into the EL layer 42, and is a layer containing a material having a highhole-injection property. Here, the EL layer 42 includes the EL layer 42a, the EL layer 42 b, the EL layer 42 c, and an EL layer 42(1) to an ELlayer 42(n).

Examples of the material having a high hole-injection property includetransition metal oxides such as molybdenum oxide, vanadium oxide,ruthenium oxide, tungsten oxide, and manganese oxide. Alternatively, itis possible to use any of the following materials: phthalocyanine-basedcompounds such as phthalocyanine (abbreviation: H₂Pc and copperphthalocyanine (abbreviation: CuPC); aromatic amine compounds such as4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation:DPAB) andN,N′-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine(abbreviation: DNTPD); high molecular compounds such aspoly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid)(abbreviation: PEDOT/PSS); and the like.

Alternatively, as the material having a high hole-injection property, acomposite material containing a hole-transport material and an acceptormaterial (electron-accepting material) can be used. In this case, theacceptor material extracts electrons from the hole-transport material,so that holes are generated in the hole-injection layer 71 and the holesare injected into the light-emitting layer 73 through the hole-transportlayer 72. Note that the hole-injection layer 71 may be formed to have asingle-layer structure using a composite material containing ahole-transport material and an acceptor material (electron-acceptingmaterial), or a stacked-layer structure in which a layer containing ahole-transport material and a layer containing an acceptor material(electron-accepting material) are stacked.

The hole-transport layer 72 is a layer transporting the holes, which areinjected from the conductive layer 41 by the hole-injection layer 71,into the light-emitting layer 73. Note that the hole-transport layer 72is a layer containing a hole-transport material. It is particularlypreferable that the HOMO level of the hole-transport material used forthe hole-transport layer 72 be the same as or close to the HOMO level ofthe hole-injection layer 71.

Examples of the acceptor material used for the hole-injection layer 71include oxides of a metal belonging to any of Group 4 to Group 8 of theperiodic table. Specific examples include molybdenum oxide, vanadiumoxide, niobium oxide, tantalum oxide, chromium oxide, tungsten oxide,manganese oxide, and rhenium oxide. Among these, molybdenum oxide isespecially preferable since it is stable in the air, has a lowhygroscopic property, and is easy to handle. Alternatively, organicacceptors such as a quinodimethane derivative, a chloranil derivative,and a hexaazatriphenylene derivative can be used. Specifically,7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F₄-TCNQ), chloranil,2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation:HAT-CN), and the like can be used.

The hole-transport materials used for the hole-injection layer 71 andthe hole-transport layer 72 are preferably substances with a holemobility greater than or equal to 10⁻⁶ cm²/Vs. Note that othersubstances can also be used as long as they have a property oftransporting more holes than electrons.

Preferred hole-transport materials are π-electron rich heteroaromaticcompounds (e.g., carbazole derivatives and indole derivatives) andaromatic amine compounds; specific examples include compounds having anaromatic amine skeleton, such as 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD),N,N-bis(3-methylphenyl)-N,N-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD),4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB), 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine(abbreviation: BPAFLP), 4-phenyl-3′-(9-phenylfluoren-9-yl)triphenylamine(abbreviation: mBPAFLP),4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation:PCBA1BP), 3-[4-(9-phenanthryl)-phenyl]-9-phenyl-9H-carbazole(abbreviation: PCPPn),N-(4-biphenyl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9-phenyl-9H-carbazol-3-amine(abbreviation: PCBiF),N-(1,1′-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine(abbreviation: PCBBiF),4,4′-diphenyl-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBBi1BP),4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBANB),4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBNBB),9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine(abbreviation: PCBAF),N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9′-bifluoren-2-amine(abbreviation: PCBASF), 4,4′,4″-tris(carbazol-9-yl)triphenylamine(abbreviation: TCTA), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine(abbreviation: TDATA), and 4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbreviation: MTDATA); compounds having acarbazole skeleton, such as 1,3-bis(N-carbazolyl)benzene (abbreviation:mCP), 4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP),3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP),3,3′-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP),3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1),3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2),3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene(abbreviation: TCPB), and9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA);compounds having a thiophene skeleton, such as4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation:DBT3P-II),2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene(abbreviation: DBTFLP-III), and4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene(abbreviation: DBTFLP-IV); and compounds having a furan skeleton, suchas 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation:DBF3P-II) and4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran(abbreviation: mmDBFFLBi-II).

High molecular compounds such as poly(N-vinylcarbazole) (abbreviation:PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA),poly[N-(4-{N-[4-(4-diphenylamino)phenyl]phenyl-N′-phenylamino}phenyl)methacrylamide](abbreviation: PTPDMA), andpoly[N,N-bis(4-butylphenyl)-N,N-bis(phenyl)benzidine] (abbreviation:Poly-TPD) can also be used.

Note that the hole-transport material is not limited to the aboveexamples, and one of or a combination of various known materials can beused as the hole-transport material for the hole-injection layer 71 andthe hole-transport layer 72. Note that the hole-transport layer 72 maybe formed of a plurality of layers. That is, a first hole-transportlayer and a second hole-transport layer may be stacked, for example.

<<Light-Emitting Layer 73>>

The light-emitting layer 73 is a layer containing a light-emittingsubstance. As the light-emitting substance, a substance whose emissioncolor is blue, violet, bluish violet, green, yellowish green, yellow,orange, red, or the like is appropriately used. Here, in the case wherethe light-emitting element 40 includes a plurality of EL layers asillustrated in FIG. 8C, the EL layers can emit different emission colorsby using different light-emitting substances in their respectivelight-emitting layers 73. Note that a stacked-layer structure in whichone light-emitting layer contains different light-emitting substancesmay be employed.

The light-emitting layer 73 may contain one or more kinds of organiccompounds (a host material and an assist material) in addition to alight-emitting substance (a guest material). As the one or more kinds oforganic compounds, one or both of the hole-transport material and theelectron-transport material can be used.

There is no particular limitation on the light-emitting substance thatcan be used for the light-emitting layer 73, and it is possible to use alight-emitting substance that converts singlet excitation energy intolight in the visible light range or a light-emitting substance thatconverts triplet excitation energy into light in the visible lightrange. Examples of the light-emitting substance are given below.

As an example of the light-emitting substance that converts singletexcitation energy into light, a substance that exhibits fluorescence(fluorescent material) can be given; examples include a pyrenederivative, an anthracene derivative, a triphenylene derivative, afluorene derivative, a carbazole derivative, a dibenzothiophenederivative, a dibenzofuran derivative, a dibenzoquinoxaline derivative,a quinoxaline derivative, a pyridine derivative, a pyrimidinederivative, a phenanthrene derivative, and a naphthalene derivative. Apyrene derivative is particularly preferable because it has a highemission quantum yield. Specific examples of the pyrene derivativeincludeN,N-bis(3-methylphenyl)-N,N-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine(abbreviation: 1,6mMemFLPAPm),N,N-diphenyl-N,N-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine(abbreviation: 1,6FLPAPm),N,N′-bis(dibenzofuran-2-yl)-N,N-diphenylpyrene-1,6-diamine(abbreviation: 1,6FrAPm),N,N′-bis(dibenzothiophen-2-yl)-N,N-diphenylpyrene-1,6-diamine(abbreviation: 1,6ThAPm),N,N′-(pyrene-1,6-diyl)bis[(N-phenylbenzo[b]naphtho[1,2-d]furan)-6-amine](abbreviation:1,6BnfAPm),N,N-(pyrene-1,6-diyl)bis[(N-phenylbenzo[b]naphtho[1,2-d]furan)-8-amine](abbreviation: 1,6BnfAPrn-02), andN,N-(pyrene-1,6-diyl)bis[(6,N-diphenylbenzo[b]naphtho[1,2-d]furan)-8-amine](abbreviation: 1,6BnfAPrn-03). In addition, pyrene derivatives arecompounds effective for meeting the chromaticity of blue in oneembodiment of the present invention.

In addition, it is possible to use5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2′-bipyridine (abbreviation:PAP2BPy), 5,6-bis[4′-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2′-bipyridine(abbreviation: PAPP2BPy),N,N-bis[4-(9H-carbazol-9-yl)phenyl]-N,N-diphenylstilbene-4,4′-diamine(abbreviation: YGA2S),4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine(abbreviation: YGAPA),4-(9H-carbazol-9-yl)-4′-(9,10-diphenyl-2-anthryl)triphenylamine(abbreviation: 2YGAPPA),N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: PCAPA),4-(10-phenyl-9-anthryl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAPA),4-[4-(10-phenyl-9-anthryl)phenyl]-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAPBA), perylene, 2,5,8,11-tetra(tert-butyl)perylene(abbreviation: TBP),N,N′-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N′,N″-triphenyl-1,4-phenylenediamine] (abbreviation: DPABPA),N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: 2PCAPPA),N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N′,N″-triphenyl-1,4-phenylenediamine(abbreviation: 2DPAPPA), or the like.

As examples of the light-emitting substance that converts tripletexcitation energy into light emission, a substance that emitsphosphorescence (phosphorescent material) and a thermally activateddelayed fluorescence (TADF) material that exhibits thermally activateddelayed fluorescence can be given.

Examples of a phosphorescent material include an organometallic complex,a metal complex (platinum complex), and a rare earth metal complex.These substances exhibit different emission colors (emission peaks), andthus are used through appropriate selection as needed.

As examples of a phosphorescent material that emits blue or green lightand whose emission spectrum has a peak wavelength at greater than orequal to 450 nm and less than or equal to 570 nm, the followingsubstances can be given.

Examples include organometallic complexes having a 4H-triazole skeleton,such astris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN²]phenyl-κC}iridium(III)(abbreviation: [Ir(mpptz-dmp)₃]),tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III)(abbreviation: [Ir(Mptz)₃]),tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(iPrptz-3b)₃]), andtris[3-(5-biphenyl)-5-isopropyl-4-phenyl-4H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(iPr5btz)₃]); organometallic complexes having a1H-triazole skeleton, such astris[3-methyl-1-(2-methylphenyl)-5-phenyl-TH-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(Mptzl-mp)₃]) andtris(1-methyl-5-phenyl-3-propyl-TH-1,2,4-triazolato)iridium(III)(abbreviation: [Ir(Prptzl-Me)₃]); organometallic complexes having animidazole skeleton, such asfac-tris[1-(2,6-diisopropylphenyl)-2-phenyl-TH-imidazole]iridium(III)(abbreviation: [Ir(iPrpmi)₃]) andtris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III)(abbreviation: [Ir(dmpimpt-Me)₃]); and organometallic complexes in whicha phenylpyridine derivative having an electron-withdrawing group is aligand, such asbis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)tetrakis(1-pyrazolyl)borate (abbreviation: FIr6),bis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III) picolinate(abbreviation: FIrpic),bis[2-(3,5-bistrifluoromethyl-phenyl)-pyridinato-N,C^(2′)]iridium(III)picolinate (abbreviation: [Ir(CF₃ppy)₂(pic)]), andbis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)acetylacetonate (abbreviation: FIr(acac)).

As examples of a phosphorescent material that emits green or yellowlight and whose emission spectrum has a peak wavelength at greater thanor equal to 495 nm and less than or equal to 590 nm, the followingsubstances can be given.

Examples include organometallic iridium complexes having a pyrimidineskeleton, such as tris(4-methyl-6-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(mppm)₃]),tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation:[Ir(tBuppm)₃]),(acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(mppm)₂(acac)]),(acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(tBuppm)₂(acac)]),(acetylacetonato)bis[6-(2-norbomyl)-4-phenylpyrimidinato]iridium(III)(abbreviation: [Ir(nbppm)₂(acac)]),(acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III)(abbreviation: [Ir(mpmppm)₂(acac)]),(acetylacetonato)bis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN3]phenyl-κC}iridium(III)(abbreviation: [Ir(dmppm-dmp)₂(acac)]), and(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)(abbreviation: [Ir(dppm)₂(acac)]); organometallic iridium complexeshaving a pyrazine skeleton, such as(acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-Me)₂(acac)]) and(acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-iPr)₂(acac)]); organometallic iridium complexeshaving a pyridine skeleton, such astris(2-phenylpyridinato-N,C^(2′))iridium(III) (abbreviation:[Ir(ppy)₃]), bis(2-phenylpyridinato-N,C^(2′))iridium(III)acetylacetonate (abbreviation: [Ir(ppy)₂(acac)]),bis(benzo[h]quinolinato)iridium(III) acetylacetonate (abbreviation:[Ir(bzq)₂(acac)]), tris(benzo[h]quinolinato)iridium(III) (abbreviation:[Ir(bzq)₃]), tris(2-phenylquinolinato-N,C^(2′))iridium(III)(abbreviation: [Ir(pq)₃]), andbis(2-phenylquinolinato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: [Ir(pq)₂(acac)]); organometallic complexes such asbis(2,4-diphenyl-1,3-oxazolato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: [Ir(dpo)₂(acac)]),bis{2-[4′-(perfluorophenyl)phenyl]pyridinato-N,C^(2′)}iridium(III)acetylacetonate (abbreviation: [Ir(p-PF-ph)₂(acac)]), andbis(2-phenylbenzothiazolato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: [Ir(bt)₂(acac)]); and rare earth metal complexes such astris(acetylacetonato) (monophenanthroline)terbium(III) (abbreviation:[Tb(acac)₃(Phen)]).

Among the above, organometallic iridium complexes having a pyridineskeleton (particularly, a phenylpyridine skeleton) or a pyrimidineskeleton are compounds effective for meeting the chromaticity of greenin one embodiment of the present invention.

As examples of a phosphorescent material that emits yellow or red lightand whose emission spectrum has a peak wavelength at greater than orequal to 570 nm and less than or equal to 750 nm, the followingsubstances can be given.

Examples include organometallic complexes having a pyrimidine skeleton,such as(diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III)(abbreviation: [Ir(5mdppm)₂(dibm)]),bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III)(abbreviation: [Ir(5mdppm)₂(dpm)]), and(dipivaloylmethanato)bis[4,6-di(naphthalen-1-yl)pyrimidinato]iridium(III)(abbreviation: [Ir(dlnpm)₂(dpm)]); organometallic complexes having apyrazine skeleton, such as(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)(abbreviation: [Ir(tppr)₂(acac)]),bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III)(abbreviation: [Ir(tppr)₂(dpm)]),bis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-P)₂(dibm)]),bis{4,6-dimethyl-2-[5-(4-cyano-2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,2,6,6-tetramethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-dmCP)₂(dpm)]),(acetylacetonato)bis[2-methyl-3-phenylquinoxalinato-N,C^(2′)]iridium(III)(abbreviation: [Ir(mpq)₂(acac)]),(acetylacetonato)bis(2,3-diphenylquinoxalinato-N,C^(2′))iridium(III)(abbreviation: [Ir(dpq)₂(acac)]), and(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(abbreviation: [Ir(Fdpq)₂(acac)]); organometallic complexes having apyridine skeleton, such astris(1-phenylisoquinolinato-N,C^(2′))iridium(III) (abbreviation:[Ir(piq)₃]) and bis(1-phenylisoquinolinato-N,C^(2′))iridium(III)acetylacetonate (abbreviation: [Ir(piq)₂(acac)]); platinum complexessuch as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrinplatinum(II)(abbreviation: [PtOEP]); and rare earth metal complexes such astris(1,3-diphenyl-1,3-propanedionato) (monophenanthroline)europium(III)(abbreviation: [Eu(DBM)₃(Phen)]) andtris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III)(abbreviation: [Eu(TTA)₃(Phen)]).

Among the above, organometallic iridium complexes having a pyrazineskeleton are compounds effective for meeting the chromaticity of red inone embodiment of the present invention. In particular, organometalliciridium complexes having a cyano group, such as [Ir(dmdppr-dmCP)₂(dpm)],are preferable because of their high stability.

Note that as the blue-light-emitting substance, a substance whosephotoluminescence peak wavelength is greater than or equal to 430 nm andless than or equal to 470 nm, preferably greater than or equal to 430 nmand less than or equal to 460 nm is used. As the green-light-emittingsubstance, a substance whose photoluminescence peak wavelength isgreater than or equal to 500 nm and less than or equal to 540 nm,preferably greater than or equal to 500 nm and less than or equal to 530nm is used. As the red-light-emitting substance, a substance whosephotoluminescence peak wavelength is greater than or equal to 610 nm andless than or equal to 680 nm, preferably greater than or equal to 620 nmand less than or equal to 680 nm is used. Note that thephotoluminescence may be measured with either a solution or a thin film.

With the parallel use of such compounds and the microcavity effect, theabove chromaticity can be met more easily. Here, a semi-transmissive andsemi-reflective electrode (a metal thin film portion) that is needed forobtaining microcavity effect preferably has a thickness of greater thanor equal to 20 nm and less than or equal to 40 nm. Further preferably,the thickness is greater than 25 nm and less than or equal to 40 nm.However, the thickness greater than 40 nm possibly reduces theefficiency.

As the organic compounds (the host material and the assist material)used in the light-emitting layer 73, one or more kinds of substanceshaving an energy gap larger than the energy gap of the light-emittingsubstance (the guest material) are used. Note that the hole-transportmaterials listed above and the electron-transport materials given belowcan be used as the host material and the assist material, respectively.

In the case where the light-emitting substance is a fluorescentmaterial, it is preferable to use, as the host material, an organiccompound that has a high energy level in a singlet excited state and hasa low energy level in a triplet excited state. For example, ananthracene derivative or a tetracene derivative is preferably used.Specific examples include9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation:PCzPA), 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation:PCPN), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation:CzPA), 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole(abbreviation: cgDBCzPA),6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,2-d]furan(abbreviation: 2mBnfPPA),9-phenyl-10-{4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4′-yl}anthracene(abbreviation: FLPPA), 5,12-diphenyltetracene, and5,12-bis(biphenyl-2-yl)tetracene.

In the case where the light-emitting substance is a phosphorescentmaterial, an organic compound having triplet excitation energy (energydifference between a ground state and a triplet excited state) higherthan that of the light-emitting substance can be selected as the hostmaterial. In this case, it is possible to use a zinc- or aluminum-basedmetal complex, an oxadiazole derivative, a triazole derivative, abenzimidazole derivative, a quinoxaline derivative, a dibenzoquinoxalinederivative, a dibenzothiophene derivative, a dibenzofuran derivative, apyrimidine derivative, a triazine derivative, a pyridine derivative, abipyridine derivative, a phenanthroline derivative, an aromatic amine, acarbazole derivative, or the like.

Specific examples include metal complexes such astris(8-quinolinolato)aluminum(III) (abbreviation: Alq),tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Almq3),bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq₂),bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III)(abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq),bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), andbis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ);heterocyclic compounds such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: TAZ),2,2′,2″-(1,3,5-benzenetriyl)-tris(1-phenyl-1H-benzimidazole)(abbreviation: TPBI), bathophenanthroline (abbreviation: BPhen),bathocuproine (abbreviation: BCP),2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation:NBphen), and 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole(abbreviation: CO11); and aromatic amine compounds such as NPB, TPD, andBSPB.

In addition, condensed polycyclic aromatic compounds such as anthracenederivatives, phenanthrene derivatives, pyrene derivatives, chrysenederivatives, and dibenzo[g,p]chrysene derivatives can be used;specifically, it is possible to use, for example,9,10-diphenylanthracene (abbreviation: DPAnth),N,N-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: CzA1PA), 4-(10-phenyl-9-anthryl)triphenylamine(abbreviation: DPhPA), YGAPA, PCAPA,N,9-diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazol-3-amine(abbreviation: PCAPBA),9,10-diphenyl-2-[N-phenyl-N-(9-phenyl-9H-carbazol-3-yl)amino]anthracene(abbreviation: 2PCAPA), 6,12-dimethoxy-5,11-diphenylchrysene,N,N,N′,N′,N″,N″,N′″,N′″-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine(abbreviation: DBC1), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole(abbreviation: CzPA),3,6-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole(abbreviation: DPCzPA), 9,10-bis(3,5-diphenylphenyl)anthracene(abbreviation: DPPA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA),2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA),9,9′-bianthryl (abbreviation: BANT),9,9′-(stilbene-3,3′-diyl)diphenanthrene (abbreviation: DPNS),9,9′-(stilbene-4,4′-diyl)diphenanthrene (abbreviation: DPNS2), or1,3,5-tri(1-pyrenyl)benzene (abbreviation: TPB3).

In the case where a plurality of organic compounds are used for thelight-emitting layer 73, compounds that form an exciplex are preferablyused in combination with a light-emitting substance. In this case,various organic compounds can be used in appropriate combination; toform an exciplex efficiently, it is particularly preferable to combine acompound that easily accepts holes (hole-transport material) and acompound that easily accepts electrons (electron-transport material). Asthe hole-transport material and the electron-transport material,specifically, any of the materials described in this embodiment can beused.

The TADF material is a material that can up-convert a triplet excitedstate into a singlet excited state (reverse intersystem crossing) usinga little thermal energy and efficiently exhibits light emission(fluorescence) from the singlet excited state. The thermally activateddelayed fluorescence is efficiently obtained under the condition wherethe difference in energy between the triplet excited level and thesinglet excited level is greater than or equal to 0 eV and less than orequal to 0.2 eV, preferably greater than or equal to 0 eV and less thanor equal to 0.1 eV Note that delayed fluorescence by the TADF materialrefers to light emission having the same spectrum as normal fluorescenceand an extremely long lifetime. The lifetime is 10⁻⁶ seconds or longer,preferably 10⁻³ seconds or longer.

Examples of the TADF material include fullerene, a derivative thereof,an acridine derivative such as proflavine, and eosin. Other examplesinclude a metal-containing porphyrin such as a porphyrin containingmagnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium(In), or palladium (Pd). Examples of the metal-containing porphyrininclude a protoporphyrin-tin fluoride complex (SnF₂(Proto IX)), amesoporphyrin-tin fluoride complex (SnF₂(Meso IX)), ahematoporphyrin-tin fluoride complex (SnF₂(Hemato IX)), a coproporphyrintetramethyl ester-tin fluoride complex (SnF₂(Copro III-4Me)), anoctaethylporphyrin-tin fluoride complex (SnF₂(OEP)), anetioporphyrin-tin fluoride complex (SnF₂(Etio I)), and anoctaethylporphyrin-platinum chloride complex (PtCl₂OEP).

Alternatively, it is possible to use a heterocyclic compound having aπ-electron rich heteroaromatic ring and a π-electron deficientheteroaromatic ring, such as2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine(PIC-TRZ),2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine(PCCzPTzn),2-[4-(10H-phenoxazin-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine(PXZ-TRZ),3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole(PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (ACRXTN),bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (DMAC-DPS), or10-phenyl-10H,10′H-spiro[acridin-9,9′-anthracen]-10′-one (ACRSA). Notethat a substance in which a π-electron rich heteroaromatic ring isdirectly bonded to a π-electron deficient heteroaromatic ring isparticularly preferable because both the donor property of theπ-electron rich heteroaromatic ring and the acceptor property of theit-electron deficient heteroaromatic ring are improved and the energydifference between the singlet excited state and the triplet excitedstate becomes small.

Note that the TADF material can also be used in combination with anotherorganic compound.

<<Electron-Transport Layer 74>>

The electron-transport layer 74 is a layer transporting the electrons,which are injected from the conductive layer 43 by theelectron-injection layer 75, to the light-emitting layer 73. Note thatthe electron-transport layer 74 is layer containing anelectron-transport material. The electron-transport material used forthe electron-transport layer 74 is preferably a substance with anelectron mobility of higher than or equal to 1×10⁻⁶ cm²/Vs. Note thatany other substance can also be used as long as the substance transportsmore electrons than holes.

Examples of the electron-transport material include metal complexeshaving a quinoline ligand, a benzoquinoline ligand, an oxazole ligand,and a thiazole ligand; an oxadiazole derivative; a triazole derivative;a phenanthroline derivative; a pyridine derivative; and a bipyridinederivative. In addition, a π-electron deficient heteroaromatic compoundsuch as a nitrogen-containing heteroaromatic compound can also be used.

Specifically, it is possible to use any of metal complexes such as Alq₃,tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Almq₃),bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq₂),BAlq, Zn(BOX)₂, and bis[2-(2-hydroxyphenyl)benzothiazolato]zinc(II)(abbreviation: Zn(BTZ)₂); heteroaromatic compounds such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),3-(4′-tert-butylphenyl)-4-phenyl-5-(4″-biphenyl)-1,2,4-triazole(abbreviation: TAZ),3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: Bphen),bathocuproine (abbreviation: BCP), and4,4′-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOS); andquinoxaline derivatives and dibenzoquinoxaline derivatives such as2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:2mDBTPDBq-II),2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTBPDBq-II),2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline(abbreviation: 2CzPDBq-III),7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:7mDBTPDBq-II), and6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:6mDBTPDBq-II).

Furthermore, a high-molecular compound such as poly(2,5-pyridinediyl)(abbreviation: PPy),poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)](abbreviation: PF-Py), orpoly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2′-bipyridine-6,6′-diyl)](abbreviation: PF-BPy) can be used.

The electron-transport layer 74 is not limited to a single layer and maybe a stack of two or more layers each containing any of the abovesubstances.

<<Electron-Injection Layer 75>>

The electron-injection layer 75 is a layer containing a substance havinga high electron-injection property. The electron-injection layer 75 canbe formed using an alkali metal, an alkaline earth metal, or a compoundthereof, such as lithium fluoride (LiF), cesium fluoride (CsF), calciumfluoride (CaF₂), or lithium oxide (LiO_(x)). A rare earth metal compoundlike erbium fluoride (ErF₃) can also be used. An electride may also beused for the electron-injection layer 75. Examples of the electrideinclude a substance in which electrons are added at high concentrationto a mixed oxide of calcium and aluminum. Any of the above-describedsubstances used for the electron-transport layer 74 can also be used.

A composite material in which an organic compound and an electron donor(donor) are mixed may also be used for the electron-injection layer 75.Such a composite material is excellent in an electron-injection propertyand an electron-transport property because electrons are generated inthe organic compound by the electron donor. The organic compound here ispreferably a material excellent in transporting the generated electrons;specifically, for example, the electron-transport material used for theelectron-transport layer 74 (e.g., a metal complex or a heteroaromaticcompound) can be used. As the electron donor, a substance showing anelectron-donating property with respect to an organic compound is used.Specifically, an alkali metal, an alkaline earth metal, and a rare earthmetal are preferable, and lithium, cesium, magnesium, calcium, erbium,ytterbium, and the like are given. In addition, an alkali metal oxideand an alkaline earth metal oxide are preferable, and lithium oxide,calcium oxide, barium oxide, and the like are given. Alternatively, aLewis base such as magnesium oxide can be used. Further alternatively,an organic compound such as tetrathiafulvalene (abbreviation: TTF) canbe used.

<<Charge-Generation Layer 44>>

The charge generation layer 44 (the charge generation layer 44 a and thecharge generation layer 44 b) has a function of injecting electrons intothe EL layer 42 on a side closer to the conductive layer 41, of the twoEL layers 42 in contact with the charge generation layer 44, andinjecting holes into the EL layer 42 on a side closer to the conductivelayer 43, when a voltage is applied between the conductive layer 41 andthe conductive layer 43. Note that the charge generation layer 44 mayhave either a structure in which an electron acceptor (acceptor) isadded to a hole-transport material or a structure in which an electrondonor (donor) is added to an electron-transport material. Alternatively,both of these structures may be stacked. Note that forming the chargegeneration layer 44 with the use of any of the above materials cansuppress an increase in drive voltage of the semiconductor device of oneembodiment of the present invention in the case where the EL layers arestacked.

When the charge generation layer 44 has a structure in which an electronacceptor is added to a hole-transport material, the electron acceptorcan be 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane(abbreviation: F₄-TCNQ), chloranil, or the like. Other examples includeoxides of metals that belong to Group 4 to Group 8 of the periodictable. Specific examples are vanadium oxide, niobium oxide, tantalumoxide, chromium oxide, molybdenum oxide, tungsten oxide, manganeseoxide, and rhenium oxide.

When the charge generation layer 44 has a structure in which an electrondonor is added to an electron-transport material, an alkali metal, analkaline earth metal, a rare earth metal, or a metal that belongs toGroup 2 or Group 13 of the periodic table, or an oxide or carbonatethereof can be used as the electron donor. Specifically, lithium (Li),cesium (Cs), magnesium (Mg), calcium (Ca), ytterbium (Yb), indium (In),lithium oxide, cesium carbonate, or the like is preferably used. Anorganic compound such as tetrathianaphthacene may be used as theelectron donor.

For fabrication of the light-emitting element 40, a vacuum process suchas an evaporation method or a solution process such as a spin coatingmethod or an ink-jet method can be used. When an evaporation method isused, a physical vapor deposition method (PVD method) such as asputtering method, an ion plating method, an ion beam evaporationmethod, a molecular beam evaporation method, or a vacuum evaporationmethod, a chemical vapor deposition method (CVD method), or the like canbe used. Specifically, the functional layers (the hole-injection layer,the hole-transport layer, the light-emitting layer, theelectron-transport layer, and the electron-injection layer) included inthe EL layer and the charge generation layer of the light-emittingelement can be formed by an evaporation method (e.g., a vacuumevaporation method), a coating method (e.g., a dip coating method, a diecoating method, a bar coating method, a spin coating method, or a spraycoating method), a printing method (e.g., an ink-jet method, a screenprinting (stencil) method, an offset printing (planography) method, aflexography (relief printing) method, a gravure printing method, or amicro-contact printing method), or the like.

Note that materials for the functional layers (the hole-injection layer,the hole-transport layer, the light-emitting layer, theelectron-transport layer, and the electron-injection layer) included inthe EL layer and the charge generation layer of the light-emittingelement described in this embodiment are not limited to the abovematerials, and other materials can be used in combination as long as thefunctions of the layers are fulfilled. For example, a high molecularcompound (e.g., an oligomer, a dendrimer, or a polymer), a middlemolecular compound (a compound between a low molecular compound and ahigh molecular compound with a molecular weight of 400 to 4000), aninorganic compound (e.g., a quantum dot material), or the like can beused. As the quantum dot material, a colloidal quantum dot material, analloyed quantum dot material, a core-shell quantum dot material, a corequantum dot material, or the like can be used.

<Cross-Sectional Structure Example 2 of Pixel>

FIG. 9 is a cross-sectional view illustrating a structure example of thepixel 10, and is a modification example of the pixel 10 having thestructure illustrated in FIG. 3. The pixel 10 having the structureillustrated in FIG. 9 is different from the pixel 10 having thestructure illustrated in FIG. 3 in that the EL layer 42 is formed byseparate coloring.

In the case of the pixel 10 having the structure illustrated in FIG. 3,the EL layer 42 emitting white light and infrared light is provided ineach pixel 10, for example. In contrast, in the case of the pixel 10having the structure illustrated in FIG. 9, the EL layer 42 emitting redlight, the EL layer 42 emitting green light, the EL layer 42 emittingblue light, and the EL layer 42 emitting infrared light are formed byseparate coloring, for example. Therefore, the filter 51 is notnecessarily provided to include a region overlapping with thelight-emitting element 40. Accordingly, light emitted from thelight-emitting element 40 can be inhibited from being absorbed by thefilter 51. Thus, the semiconductor device of one embodiment of thepresent invention can emit high-luminance light and the semiconductordevice of one embodiment of the present invention can have reduced powerconsumption. Note that also in the pixel 10 having the structureillustrated in FIG. 9, the filter 51 may be provided to include a regionoverlapping with the light-emitting element 40. In this case, thesemiconductor device of one embodiment of the present invention can emitlight with higher color purity.

FIG. 10A is a cross-sectional view illustrating a structure example ofthe pixel 10, and is a modification example of the pixel 10 having thestructure illustrated in FIG. 3. The pixel 10 having the structureillustrated in FIG. 10A is different from the pixel 10 having thestructure illustrated in FIG. 3 in that the conductive layer 31 is notformed over the back surface of the substrate 11 and a low-resistanceregion 34 is formed on the back surface side of the substrate 11.

The low-resistance region 34 can be formed in such a manner that theback surface of the substrate 11 is polished as illustrated in FIG. 6Aand then impurities are added to the back surface of the substrate 11.For example, adding a trivalent element can make the low-resistanceregion 34 a p-type region, and adding a pentavalent element can make thelow-resistance region 34 an n-type region. Note that the low-resistanceregion 34 can be a p-type region in the case where the substrate 11 is ap-type substrate, and the low-resistance region 34 can be an n-typeregion in the case where the substrate 11 is an n-type substrate.Examples of the method for adding the above impurities include an ionimplantation method, an ion doping method, and a plasma immersion ionimplantation method.

FIG. 10B is a cross-sectional view illustrating a structure example ofthe pixel 10, and is a modification example of the pixel 10 having thestructure illustrated in FIG. 3. The pixel 10 having the structureillustrated in FIG. 10B is different from the pixel 10 having thestructure illustrated in FIG. 3 in that a microlens 55 is provided inthe layer 63.

The microlens 55 is provided to include a region overlapping with thephotoelectric conversion element 12. Accordingly, light is incident onthe photoelectric conversion element 12 in a vertical direction, so thatthe photoelectric conversion element 12 can have higher light detectionsensitivity.

Although the microlens 55 is provided to be covered with the insulatinglayer 32 in FIG. 10B, one embodiment of the present invention is notlimited thereto. For example, the microlens 55 may be provided to becovered with the insulating layer 33. Alternatively, a microlens arraymay be provided both in the layer 63 and over the layer 63 (see FIG. 4).

<Cross-Sectional Structure Example 3 of Pixel>

FIG. 11 is a cross-sectional view illustrating a structure example ofthe pixel 10. In the pixel 10 having the structure illustrated in FIG.11, the transistor 101, the transistor 132, the photoelectric conversionelement 12, the light-emitting element 40, and the like are providedbetween a substrate 60 and the substrate 50.

The pixel 10 having the structure illustrated in FIG. 11 can have astacked-layer structure of the layer 61 and a layer 64. In the layer 61,the substrate 60, the insulating layer 86, the insulating layer 80, thetransistor 101, the transistor 132, and the insulating layer 82 areprovided. The transistor 101 and the transistor 132 are provided betweenthe insulating layer 80 and the insulating layer 82. The insulatinglayer 85 and the insulating layer 84 are provided to cover the channelformation regions, the source regions, and the drain regions of thetransistor 101 and the transistor 132. In addition, the insulating layer83 is provided between the insulating layer 84 and the insulating layer82.

The conductive layer 21 is provided to be electrically connected to oneof the source and the drain of the transistor 101, and the conductivelayer 22 is provided to be electrically connected to the other of thesource and the drain of the transistor 101. The conductive layer 23 isprovided to be electrically connected to one of the source and the drainof the transistor 132, and the conductive layer 24 is provided to beelectrically connected to the other of the source and the drain of thetransistor 132.

As the substrate 60, a silicon substrate, a glass substrate, a ceramicssubstrate, a resin substrate, or the like can be used. Note that atransistor or the like can be provided between the substrate 60 and thetransistors 101 and 132. For example, in the case where a siliconsubstrate is used as the substrate 60, a Si transistor can be provided.

In the layer 64, the insulating layer 32, the light-emitting element 40,the photoelectric conversion element 12, and the insulating layer 33 areprovided. The substrate 50 and the filter 51 are also provided in thelayer 64. The substrate 50 and the substrate 60 are sealed with thesealing layer 52.

The insulating layer 32 is provided to cover the conductive layer 21 tothe conductive layer 24, and the light-emitting element 40 and thephotoelectric conversion element 12 are provided over the insulatinglayer 32.

The light-emitting element 40 has a stacked-layer structure in which theconductive layer 41, the EL layer 42, and the conductive layer 43 arestacked in this order from the insulating layer 32 side. Thephotoelectric conversion element 12 has a structure in which aconductive layer 45, an active layer 46, and the conductive layer 43 arestacked in this order from the insulating layer 32 side.

Here, the conductive layer 41 and the conductive layer 45 can be formedthrough the same process. Specifically, an insulating film is formedover the conductive layer 21 to the conductive layer 24 and theinsulating layer 82, and an opening portion reaching the conductivelayer 21 and an opening portion reaching the conductive layer 23 areprovided in the insulating film, whereby the insulating layer 32 isformed. Next, a conductive film is formed over the insulating layer 32and in the opening portion, and then patterning is performed by aphotolithography method or the like. Then, the conductive film isprocessed along the formed pattern by an etching method or the like. Inthe above manner, the conductive layer 41 and the conductive layer 45can be formed.

The conductive layer 43 can serve as both the common electrode of thelight-emitting element 40 and the common electrode of the photoelectricconversion element 12. Thus, when the pixel 10 has the structureillustrated in FIG. 11, the fabrication process of the semiconductordevice of one embodiment of the present invention can be simplified.Therefore, the semiconductor device of one embodiment of the presentinvention can be inexpensive.

The conductive layer 41 is electrically connected to the conductivelayer 23 through the opening provided in the insulating layer 32. Theconductive layer 45 is electrically connected to the conductive layer 21through the opening provided in the insulating layer 32. The insulatinglayer 33 is provided to cover an end of the conductive layer 41 and anend of the conductive layer 45.

For the conductive layer 41 and the conductive layer 45, alow-resistance conductive film of a metal or the like can be used. Forexample, the conductive layer 41 and the conductive layer 45 can beformed using one or more kinds of metals such as tungsten (W),molybdenum (Mo), zirconium (Zr), hafnium (Hf), vanadium (V), niobium(Nb), tantalum (Ta), chromium (Cr), cobalt (Co), nickel (Ni), titanium(Ti), platinum (Pt), aluminum (Al), copper (Cu), and silver (Ag); alloysthereof; and metal nitrides thereof.

The conductive layer 45 has a function of an electrode of thephotoelectric conversion element 12. Thus, it can be said that oneelectrode of the photoelectric conversion element 12 is electricallyconnected to one of the source and the drain of the transistor 101through the conductive layer 21.

The active layer 46 can have a stacked-layer structure in which a p-typesemiconductor and an n-type semiconductor are stacked to form a pnjunction; or a stacked-layer structure in which a p-type semiconductor,an i-type semiconductor, and an n-type semiconductor are stacked to forma pin junction, for example.

As the semiconductor used for the active layer 46, an inorganicsemiconductor such as silicon or an organic semiconductor containing anorganic compound can be used. It is particularly preferable to use anorganic semiconductor material because the EL layer 42 of thelight-emitting element 40 and the active layer 46 can be formed with thesame manufacturing apparatus.

In the case where an organic semiconductor material is used for theactive layer 46, an electron-accepting organic semiconductor materialsuch as fullerene (e.g., C₆₀ or C₇₀) or its derivative can be used as ann-type semiconductor material. As a p-type semiconductor material, anelectron-donating organic semiconductor material such as copper(II)phthalocyanine (abbreviation: CuPc) or5,10,15,20-tetraphenylbisbenzo[5,6]indeno[1,2,3-cd:1′,2′,3′-lm]perylene(abbreviation: DBP) can be used. The active layer 46 may have astacked-layer structure (a p-n stacked-layer structure) including anelectron-accepting semiconductor material and an electron-donatingsemiconductor material, or a stacked-layer structure (a p-i-nstacked-layer structure) in which a bulk heterostructure layer formed byco-evaporation of an electron-accepting semiconductor material and anelectron-donating semiconductor material is provided therebetween.Furthermore, a layer functioning as a hole-blocking layer or a layerfunctioning as an electron-blocking layer may be provided around (aboveor below) the p-n stacked-layer structure or the p-i-n stacked-layerstructure, in order to inhibit dark current caused when light is notapplied.

In the case where the pixel 10 has the structure illustrated in FIG. 11,it is unnecessary to provide the substrate 11 in the pixel 10. Thus,when a substrate having flexibility (hereinafter also referred to as aflexible substrate) is used as the substrate 60 and the substrate 50,for example, the semiconductor device of one embodiment of the presentinvention can be a semiconductor device having flexibility.

The flexible substrate is preferably a substrate using a film,particularly preferably a substrate using a resin film. In this case,the semiconductor device of one embodiment of the present invention canhave higher flexibility and can be reduced in weight and thickness.

For the flexible substrate, a polyester resin such as polyethyleneterephthalate (PET) or polyethylene naphthalate (PEN), apolyacrylonitrile resin, an acrylic resin, a polyimide resin, apolymethyl methacrylate resin, a polycarbonate (PC) resin, a polyethersulfone (PES) resin, a polyamide resin (e.g., nylon or aramid), apolysiloxane resin, a cycloolefin resin, a polystyrene resin, apolyamide-imide resin, a polyurethane resin, a polyvinyl chloride resin,a polyvinylidene chloride resin, a polypropylene resin, apolytetrafluoroethylene (PTFE) resin, an ABS resin, or cellulosenanofiber can be used, for example. Alternatively, glass that is thinenough to have flexibility may be used.

<Circuit Configuration Example of Pixel>

FIG. 12 is a circuit diagram illustrating a configuration example of thepixel 10. The pixel 10 includes the imaging circuit 100 provided withthe photoelectric conversion element 12 and a display circuit 130provided with the light-emitting element 40.

<<Circuit Configuration Example of Imaging Circuit>>

The imaging circuit 100 includes the transistor 101, a transistor 102, atransistor 103, a transistor 104, and a capacitor 105 in addition to thephotoelectric conversion element 12. Note that a configuration in whichthe capacitor 105 is not provided may be employed.

One electrode of the photoelectric conversion element 12 is electricallyconnected to one of the source and the drain of the transistor 101. Theone of the source and the drain of the transistor 101 is electricallyconnected to one of a source and a drain of the transistor 102. The oneof the source and the drain of the transistor 102 is electricallyconnected to a gate of the transistor 103. The gate of the transistor103 is electrically connected to one electrode of the capacitor 105. Oneof a source and a drain of the transistor 103 is electrically connectedto one of a source and a drain of the transistor 104.

A node where the one of the source and the drain of the transistor 101,the one of the source and the drain of the transistor 102, the gate ofthe transistor 103, and the one electrode of the capacitor 105 areconnected is a node FD. The node FD can function as a chargeaccumulation portion.

A gate of the transistor 101 is electrically connected to a wiring 111.A gate of the transistor 102 is electrically connected to a wiring 112.A gate of the transistor 104 is electrically connected to a wiring 114.The other electrode of the photoelectric conversion element 12 iselectrically connected to a wiring 121. The other of the source and thedrain of the transistor 102 is electrically connected to a wiring 122.The other of the source and the drain of the transistor 104 iselectrically connected to a wiring 124. The other electrode of thecapacitor 105 is electrically connected to a wiring 125.

The wiring 111, the wiring 112, and the wiring 114 each have a functionof a scan line, and the conduction of the transistors can be controlledwith signals supplied to the gates of the transistors through the wiring111, the wiring 112, and the wiring 114. The wiring 124 has a functionof a data line, and imaging data obtained by the photoelectricconversion element 12 is output to the outside of the imaging circuit100 through the wiring 124.

The wiring 121, the wiring 122, and the wiring 125 each have a functionof a power supply line. The imaging circuit 100 illustrated in FIG. 12has a configuration in which the cathode of the photoelectric conversionelement 12 is electrically connected to one of the source and the drainof the transistor 101 and the anode of the photoelectric conversionelement 12 is electrically connected to the wiring 121. Thus, the nodeFD can be reset to a high potential in the operation with the wiring 121being set to a low potential and the wiring 122 being set to a highpotential, so that the photoelectric conversion element 12 can beoperated with a reverse bias. Note that the wiring 125 can be set to alow potential.

In this specification and the like, a high potential refers to apotential higher than a low potential. For example, the high potentialcan be a positive potential and the low potential can be a groundpotential or a negative potential.

The transistor 101 has a function of a transfer transistor. When thetransistor 101 is brought into a conduction state, the potential of thenode FD can be set to a potential corresponding to the amount of lightexposure to the photoelectric conversion element 12. Thus, the imagingcircuit 100 can obtain imaging data.

The transistor 102 has a function of a reset transistor. When thetransistor 102 is brought into a conduction state, the potential of thenode FD can be reset to the potential of the wiring 122.

The transistor 103 has a function of an amplifier transistor and canperform output in accordance with the potential of the node FD.

The transistor 104 has a function of a selection transistor. When thetransistor 104 is brought into a conduction state, imaging data can beoutput to the wiring 124. Specifically, the current of the wiring 124can have a value corresponding to the imaging data.

<<Configuration Example of Display Circuit>>

The display circuit 130 includes a transistor 131, the transistor 132, atransistor 133, and a capacitor 134 in addition to the light-emittingelement 40.

One of a source and a drain of the transistor 131 is electricallyconnected to a gate of the transistor 132. The gate of the transistor132 is electrically connected to one electrode of the capacitor 134. Oneof a source and a drain of the transistor 132 is electrically connectedto one of a source and a drain of the transistor 133. The one of thesource and the drain of the transistor 133 is electrically connected tothe other electrode of the capacitor 134. The other electrode of thecapacitor 134 is electrically connected to one electrode of thelight-emitting element 40.

The other of the source and the drain of the transistor 131 iselectrically connected to a wiring 141. The other of the source and thedrain of the transistor 132 is electrically connected to a wiring 142.The other of the source and the drain of the transistor 133 iselectrically connected to a wiring 143. A gate of the transistor 131 anda gate of the transistor 133 are electrically connected to a wiring 144.The other electrode of the light-emitting element 40 is electricallyconnected to a wiring 145.

The wiring 141 has a function of a data line, and data includinginformation on the emission luminance of the light-emitting element 40is supplied to the display circuit 130 through the wiring 141. Thewiring 143 has a function of a monitor line, and the electricalcharacteristics or the like of the light-emitting element 40 can bedetected by detection of current flowing through the wiring 143, forexample. The wiring 144 has a function of a scan line, and theconduction of the transistor 131 and the transistor 133 can becontrolled with signals supplied to the gates of the transistor 131 andthe transistor 133 through the wiring 144.

The wiring 142 and the wiring 145 each have a function of a power supplyline. The display circuit 130 illustrated in FIG. 12 has a configurationin which the anode of the light-emitting element 40 is electricallyconnected to one of the source and the drain of the transistor 132 andthe cathode of the light-emitting element 40 is electrically connectedto the wiring 145. Thus, the light-emitting element 40 can be operatedwith a forward bias with the wiring 142 being set to a high potentialand the wiring 145 being set to a low potential, so that current whoseamount corresponds to data supplied to the display circuit 130 can flowinto the light-emitting element 40. Thus, the light-emitting element 40can emit light with a luminance corresponding to the data supplied tothe display circuit 130.

When the transistor 131 is brought into a conduction state in thedisplay circuit 130 having the configuration illustrated in FIG. 12, thegate potential of the transistor 132 can be a potential corresponding todata supplied through the wiring 141. Thus, the data can be written tothe display circuit 130.

The transistor 132 has a function of a driving transistor, and currentflowing into the light-emitting element 40 can be controlled inaccordance with a potential supplied to the transistor.

When the transistor 133 is brought into a conduction state, current canflow through the wiring 143. Thus, the electrical characteristics or thelike of the light-emitting element 40 can be obtained.

FIG. 12 illustrates a configuration in which the imaging circuit 100 andthe display circuit 130 are not electrically connected to each other. Inthis case, the imaging circuit 100 and the display circuit 130 can becontrolled independently. Note that in the case where the imagingcircuit 100 and the display circuit 130 are electrically connected toeach other, the operation of the imaging circuit 100 and the operationof the display circuit 130 can be controlled dependently on each other.

<Configuration Example of Semiconductor Device>

FIG. 13A is a block diagram illustrating a configuration example of asemiconductor device of one embodiment of the present invention. Thesemiconductor device includes the pixel array 151 including the pixels10 arranged in a matrix, a gate driver circuit 152, and a source drivercircuit 153. The imaging circuit 100 and the display circuit 130 areprovided in the pixel 10.

The gate driver circuit 152 has a function of selecting a row of thepixel array 151. The source driver circuit 153 has a function ofgenerating data that is to be supplied to the display circuit 130. Inaddition, the source driver circuit 153 has a function of receivingimaging data obtained by the imaging circuit 100 and outputting theimaging data to the outside of the semiconductor device.

Although all the pixels 10 include both the imaging circuit 100 and thedisplay circuit 130 in the semiconductor device illustrated in FIG. 13A,one embodiment of the present invention is not limited thereto. FIG. 13Bis a diagram illustrating a configuration example of the pixel array151, and is a modification example of the pixel array 151 having theconfiguration illustrated in FIG. 13A. The pixel array 151 having theconfiguration illustrated in FIG. 13B is different from the pixel array151 having the configuration illustrated in FIG. 13A in that the imagingcircuits 100 are provided only in some of the pixels 10.

In the semiconductor device including the pixel array 151 having theconfiguration illustrated in FIG. 13B, the opening area of the displaycircuit 130 can be increased. Thus, the semiconductor device of oneembodiment of the present invention can emit high-luminance light andthe semiconductor device of one embodiment of the present invention canhave reduced power consumption.

As the transistor 101 and the transistor 102 included in the imagingcircuit 100 illustrated in FIG. 12 and the like, OS transistors arepreferably used. The OS transistor has a feature of an extremely lowoff-state current. When OS transistors are used as the transistor 101and the transistor 102, a period during which charge can be retained atthe node FD can be elongated greatly. Therefore, a global shutter systemin which a charge accumulation operation is performed in all the pixelsat the same time can be used without complicating the circuitconfiguration and operation method.

FIG. 14A is a schematic view of an operation method with a rollingshutter system, and FIG. 14B is a schematic view of a global shuttersystem. Note that En denotes exposure (accumulation operation) in ann-th column (n is a natural number), and Rn denotes reading operation inthe n-th column. FIG. 14A and FIG. 14B each show an operation from afirst row (Line[1]) to an M-th row (Line[M]) (M is a natural number).

The rolling shutter system is an operation method in which the lightexposure and data reading are performed sequentially and a readingperiod of a row overlaps with a light exposure period of another row.The reading operation is performed immediately after the light exposure,so that imaging can be performed even with a circuit configurationhaving a relatively short data retention period. However, one frameimage is formed with imaging data obtained not simultaneously, resultingin a distorted image in the case of imaging a moving object.

In contrast, the global shutter system is an operation method in whichlight exposure is performed on all the pixels simultaneously, data isretained in each pixel, and data reading is performed row by row. Thus,an image without distortion can be obtained even in the case of imaginga moving object.

In the case where a transistor with a relatively high off-state current,such as a Si transistor, is used in a pixel, a rolling shutter system isused because charges easily leak from a charge accumulation portion. Inorder to achieve a global shutter system using a Si transistor, it isnecessary to separately provide a memory circuit or the like and toperform more complicated operation at high speed. In contrast, in thecase where an OS transistor is used in a pixel, there is little chargeleakage from the charge accumulation portion, so that the global shuttersystem can be easily achieved.

Note that OS transistors may be used also as the transistor 103 and thetransistor 104. Furthermore, OS transistors may be used also as thetransistor 131 to the transistor 133 included in the display circuit130. When one kind of transistor such as OS transistor is used as allthe transistors included in the semiconductor device of one embodimentof the present invention, the fabrication process of the semiconductordevice of one embodiment of the present invention can be simplified.Therefore, the semiconductor device of one embodiment of the presentinvention can be inexpensive. Note that all or some of the transistor101 to the transistor 104 and the transistor 131 to the transistor 133may be Si transistors. Examples of the Si transistor include atransistor containing amorphous silicon and a transistor containingcrystalline silicon (typically, low-temperature polysilicon, singlecrystal silicon, or the like).

FIG. 15 is a circuit diagram illustrating a configuration example of thepixel 10, and is a modification example of the pixel 10 having theconfiguration illustrated in FIG. 12. The pixel 10 having theconfiguration illustrated in FIG. 15 is different from the pixel 10having the configuration illustrated in FIG. 12 in that the otherelectrode of the capacitor 105 included in the imaging circuit 100 iselectrically connected to the wiring 155 having a function of a dataline, not to the wiring 125 having a function of a power supply line.

In the imaging circuit 100 having the configuration illustrated in FIG.15, data can be supplied to the other electrode of the capacitor 105through the wiring 155. The data can be added to imaging data obtainedusing the photoelectric conversion element 12. Thus, imaging dataobtained by the imaging circuit 100 can be corrected, for example. Theimaging data obtained by the imaging circuit 100 can be subjected toimaging processing such as noise removal, for example.

Note that the imaging circuit 100 illustrated in FIG. 15 has aconfiguration in which the anode of the photoelectric conversion element12 is electrically connected to one of the source and the drain of thetransistor 101, and the cathode of the photoelectric conversion element12 is electrically connected to the wiring 121. Thus, the node FD can bereset to a low potential in the operation with the wiring 121 being setto a high potential and the wiring 122 being set to a low potential, sothat the photoelectric conversion element 12 can be operated with areverse bias.

FIG. 16 is a block diagram illustrating a configuration example of thesemiconductor device of one embodiment of the present invention, and isa modification example of the semiconductor device having theconfiguration illustrated in FIG. 13A. The semiconductor device havingthe configuration illustrated in FIG. 16 is different from thesemiconductor device having the configuration illustrated in FIG. 13A inincluding a data generation circuit 154.

The pixel 10 having the configuration illustrated in FIG. 15 can be usedas the pixel 10 illustrated in FIG. 16. The wiring 155 electricallyconnected to the imaging circuit 100 is electrically connected to thedata generation circuit 154. The data generation circuit 154 has afunction of generating data that is to be supplied to the imagingcircuit 100. Data generated by the data generation circuit 154 issupplied to the imaging circuit 100 through the wiring 155.Specifically, data generated by the data generation circuit 154 issupplied to the other electrode of the capacitor 105 included in theimaging circuit 100 through the wiring 155.

FIG. 17 is a timing chart showing an example of an operation method ofthe imaging circuit 100 having the configuration illustrated in FIG. 15.Note that in the timing chart in this specification, “H” represents ahigh potential and “L” represents a low potential.

In a period T1, the potential of the wiring 111 and the potential of thewiring 112 are each set to a high potential and the potential of thewiring 114 is set to a low potential, whereby the transistor 101 and thetransistor 102 are turned on and the transistor 104 is turned off.Accordingly, the potential of the node FD is reset to a low potentialthat is the potential of the wiring 122. The potential of the wiring 155is a potential V_(ref) that is a reference potential. The potentialV_(ref) can be a ground potential, for example. Hereinafter, thepotential V_(ref) is a ground potential.

In a period T2, the potential of the wiring 111 is set to a highpotential, and the potential of the wiring 112 and the potential of thewiring 114 are each set to a low potential, whereby the transistor 101is turned on and the transistor 102 and the transistor 104 are turnedoff. Accordingly, the potential of the node FD increases in accordancewith the amount of light exposure to the photoelectric conversionelement 12. Note that the potential of the wiring 155 is kept at thepotential V_(ref).

In a period T3, the potential of the wiring 111, the potential of thewiring 112, and the potential of the wiring 114 are each set to a lowpotential, whereby the transistor 101, the transistor 102, and thetransistor 104 are turned off. Accordingly, the potential of the node FDis determined and retained. In the above manner, imaging data isobtained. Here, the determined potential of the node FD is referred toas a potential V₁. Note that the potential of the wiring 155 is kept atthe potential V_(ref).

Using OS transistors with a low off-state current as the transistor 101and the transistor 102 that are electrically connected to the node FDcan suppress charge leakage from the node FD, and thus enables alonger-term retention of the imaging data obtained by the imagingcircuit 100.

In a period T4, the potential of the wiring 111 and the potential of thewiring 112 are each set to a low potential and the potential of thewiring 114 is set to a high potential, whereby the transistor 101 andthe transistor 102 are turned off and the transistor 104 is turned on.Accordingly, a current I_(ref) represented by Formula (1) below flowsthrough the wiring 124. Here, k is a proportionality constant and V_(th)is the threshold voltage of the transistor 103. Note that the potentialof the wiring 155 is kept at the potential V_(ref).

[Formula 1]

I _(ref) =k(V ₁ −V _(th))²  (1)

Then, in a period T5, the potential of the wiring 155 is set to apotential corresponding to data generated by the data generation circuit154 illustrated in FIG. 16. When the potential is a potential V₂ and thecapacitive coupling coefficient of the node FD is 1, the potential ofthe node FD is a potential “V₁+V₂”. Accordingly, a current I representedby Formula (2) below flows through the wiring 124.

[Formula 2]

I=k(V ₁ +V ₂ −V _(th))²  (2)

After the current flowing through the wiring 124 takes a valuerepresented by Formula (2), “I_(ref)−I” is calculated. The arithmeticoperation can be performed using an arithmetic circuit (not illustratedin FIG. 16 or the like), for example. Note that hereinafter “I_(ref)−I”is expressed as ΔI.

$\begin{matrix}\left\lbrack {{Formula}\mspace{20mu} 3} \right\rbrack & \; \\\begin{matrix}{{\Delta\; I} = {I_{ref} - I}} \\{= {k\left\{ {\left( {V_{1} - V_{th}} \right)^{2} - \left( {V_{1} + V_{2} - V_{th}} \right)^{2}} \right\}}} \\{= {k\left( {V_{1} - V_{th} + V_{1} + V_{2} - V_{th}} \right)}} \\{\left( {V_{1} - V_{th} - V_{1} - V_{2} + V_{th}} \right)} \\{= {{- k}\;{V_{2}\left( {{2V_{1}} + V_{2} - {2V_{th}}} \right)}}}\end{matrix} & (3)\end{matrix}$

Next, a value obtained by subtracting ΔI₀, which is “I_(ref)−I” withoutlight exposure, from ΔI shown in Formula (3) is calculated. That is,“ΔI−ΔI₀” is calculated. The arithmetic operation can be performed usingthe arithmetic circuit or the like. Here, ΔI₀ can be represented byFormula (4) below. Note that the potential of the node FD when thecurrent flowing through the wiring 124 is ΔI₀ is the potential of thewiring 122, and the potential is a ground potential.

$\begin{matrix}\left\lbrack {{Formula}\mspace{20mu} 4} \right\rbrack & \; \\\begin{matrix}{{\Delta\; I_{0}} = {k\left\{ {\left( {- V_{th}} \right)^{2} - \left( {V_{2} - V_{th}} \right)^{2}} \right\}}} \\{= {{k\left( {{- V_{th}} + V_{2} - V_{th}} \right)}\left( {{- V_{th}} - V_{2} + V_{th}} \right)}} \\{= {{- k}\;{V_{2}\left( {V_{2} - {2V_{th}}} \right)}}}\end{matrix} & (4)\end{matrix}$

Thus, the “ΔI−ΔI₀” can be represented by Formula (5) below.

$\begin{matrix}\left\lbrack {{Formula}\mspace{20mu} 5} \right\rbrack & \; \\\begin{matrix}{{{\Delta\; I} - {\Delta\; I_{0}}} = {k\left\{ {{- {V_{2}\left( {{2V_{1}} + V_{2} - {2V_{th}}} \right)}} + {V_{2}\left( {V_{2} - {2V_{th}}} \right)}} \right\}}} \\{= {{- 2}k\; V_{1}V_{2}}}\end{matrix} & (5)\end{matrix}$

As described above, the value of current flowing through the wiring 124corresponds to the product of the potential V₁ corresponding to imagingdata obtained by the imaging circuit 100 and the potential V₂corresponding to data supplied from the data generation circuit 154 tothe imaging circuit 100. Thus, the data supplied from the datageneration circuit 154 to the imaging circuit 100 can be added to theimaging data obtained by the imaging circuit 100. The above is theoperation in the period T5.

In a period T6, the potentials of the wiring 111, the wiring 112, andthe wiring 114 are each set to a low potential. Accordingly, thetransistor 101, the transistor 102, and the transistor 104 are turnedoff. The above is the example of the operation method of the imagingcircuit 100 having the configuration illustrated in FIG. 15.

<Structure Example of Transistor>

FIG. 18A illustrates a detailed structure example of an OS transistorthat can be used as the transistor 101 or the like. The OS transistorillustrated in FIG. 18A has a self-aligned structure in which aninsulating layer is provided over a stack of a metal oxide layer and aconductive layer, and a groove reaching the metal oxide layer isprovided in the insulating layer and the conductive layer to form asource electrode 205 and a drain electrode 206.

The OS transistor can have a structure including a gate electrode 201, agate insulating layer 202, and a back gate electrode 235 in addition toa channel formation region 210, a source region 203, and a drain region204 that are formed in a metal oxide layer 207. At least the gateinsulating layer 202 and the gate electrode 201 are provided in thegroove. A metal oxide layer 208 may be further provided in the groove.In addition, the insulating layer 85 has a function of a gate insulatinglayer of the back gate electrode 235.

As illustrated in FIG. 18B, the OS transistor may have a self-alignedstructure in which the source region 203 and the drain region 204 areformed in the metal oxide layer using the gate electrode 201 as a mask.

Alternatively, as illustrated in FIG. 18C, the OS transistor may be anon-self-aligned top-gate transistor including a region where the gateelectrode 201 overlaps with the source electrode 205 or the drainelectrode 206.

As illustrated in the cross-sectional view of the transistor in thechannel width direction in FIG. 18D, the back gate electrode 235 may beelectrically connected to the gate electrode 201 that is a front gate ofthe transistor, which is provided to face the back gate. Note that FIG.18D illustrates the transistor in FIG. 18A as an example, but the sameapplies to transistors having other structures. The back gate electrode235 may be supplied with a fixed potential that is different from thatsupplied to the front gate.

This embodiment can be combined with any of the other embodiments asappropriate.

Embodiment 3

In this embodiment, the composition of a CAC (Cloud-AlignedComposite)-OS that can be used for a transistor disclosed in oneembodiment of the present invention will be described.

The CAC-OS is, for example, a composition of a material in whichelements that constitute a metal oxide are unevenly distributed to havea size of greater than or equal to 0.5 nm and less than or equal to 10nm, preferably greater than or equal to 1 nm and less than or equal to 2nm, or a similar size. Note that in the following description, a statein which one or more metal elements are unevenly distributed and regionsincluding the metal element(s) are mixed to have a size of greater thanor equal to 0.5 nm and less than or equal to 10 nm, preferably greaterthan or equal to 1 nm and less than or equal to 2 nm, or a similar sizein a metal oxide is referred to as a mosaic pattern or a patch-likepattern.

Note that the metal oxide preferably contains at least indium. Inparticular, indium and zinc are preferably contained. Moreover, inaddition to these, one kind or a plurality of kinds selected fromaluminum, gallium, yttrium, copper, vanadium, beryllium, boron, silicon,titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum,cerium, neodymium, hafnium, tantalum, tungsten, magnesium, and the likemay be contained.

For example, a CAC-OS in an In—Ga—Zn oxide (an In—Ga—Zn oxide in theCAC-OS may be particularly referred to as CAC-IGZO) has a composition inwhich materials are separated into indium oxide (hereinafter referred toas InO_(X1) (X1 is a real number greater than 0)), indium zinc oxide(hereinafter referred to as In_(X2)Zn_(Y2)O_(Z2) (each of X2, Y2, and Z2is a real number greater than 0)), or the like and gallium oxide(hereinafter referred to as GaO_(X3) (X3 is a real number greater than0)), gallium zinc oxide (hereinafter referred to as Ga_(X4)Zn_(Y4)O_(Z4)(each of X4, Y4, and Z4 is a real number greater than 0)), or the likeso that a mosaic pattern is formed, and mosaic-like InO_(X1) orIn_(X2)Zn_(Y2)O_(Z2) is evenly distributed in the film (this compositionis hereinafter also referred to as a cloud-like composition).

That is, the CAC-OS is a composite metal oxide with a composition inwhich a region including GaO_(X3) as a main component and a regionincluding In_(X2)Zn_(Y2)O_(Z2) or InO_(X1) as a main component aremixed. Note that in this specification, when the atomic ratio of In toan element M in a first region is greater than the atomic ratio of In toan element M in a second region, for example, the first region isdescribed as having higher In concentration than the second region.

Note that IGZO is a common name and sometimes refers to one compoundformed of In, Ga, Zn, and O. A typical example is a crystalline compoundrepresented by InGaO₃ (ZnO)_(m1) (m1 is a natural number) and acrystalline compound represented by In_((1+x0))Ga_((1-x0))O₃(ZnO)_(m0)(−1≤x0≤1; m0 is a given number).

The above crystalline compound has a single crystal structure, apolycrystalline structure, or a CAAC (C-Axis Aligned Crystalline)structure. Note that the CAAC structure is a crystal structure in whicha plurality of IGZO nanocrystals have c-axis alignment and are connectedin the a-b plane direction without alignment.

Meanwhile, the CAC-OS relates to the material composition of a metaloxide. In the material composition of a CAC-OS containing In, Ga, Zn,and O, some regions that contain Ga as a main component and are observedas nanoparticles and some regions that contain In as a main componentand are observed as nanoparticles are each randomly dispersed in amosaic pattern. Therefore, the crystal structure is a secondary elementfor the CAC-OS.

Note that in the CAC-OS, a stacked-layer structure including two or morekinds of films with different atomic ratios is not included. Forexample, a two-layer structure of a film containing In as a maincomponent and a film containing Ga as a main component is not included.

A boundary between the region including GaO_(X3) as a main component andthe region including In_(X2)Zn_(Y2)O_(Z2) or InO_(X1) as a maincomponent is not clearly observed in some cases.

Note that in the case where one kind or a plurality of kinds selectedfrom aluminum, yttrium, copper, vanadium, beryllium, boron, silicon,titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum,cerium, neodymium, hafnium, tantalum, tungsten, magnesium, and the likeare contained instead of gallium, the CAC-OS refers to a composition inwhich some regions that contain the metal element(s) as a main componentand are observed as nanoparticles and some regions that contain In as amain component and are observed as nanoparticles are each randomlydispersed in a mosaic pattern.

The CAC-OS can be formed by a sputtering method under a condition wherea substrate is not heated intentionally, for example. In the case offorming the CAC-OS by a sputtering method, one or more selected from aninert gas (typically, argon), an oxygen gas, and a nitrogen gas may beused as a deposition gas. The ratio of the flow rate of the oxygen gasto the total flow rate of the deposition gas in deposition is preferablyas low as possible; for example, the flow rate ratio of the oxygen gasis higher than or equal to 0% and lower than 30%, preferably higher thanor equal to 0% and lower than or equal to 10%.

The CAC-OS is characterized in that a clear peak is not observed whenmeasurement is conducted using a θ/2θ scan by an out-of-plane method,which is an X-ray diffraction (XRD) measurement method. That is, it isfound from the X-ray diffraction measurement that no alignment in thea-b plane direction and the c-axis direction is observed in the measuredregion.

In an electron diffraction pattern of the CAC-OS which is obtained byirradiation with an electron beam with a probe diameter of 1 nm (alsoreferred to as a nanobeam electron beam), a ring-like region with highluminance (a ring region) and a plurality of bright spots in the ringregion are observed. Thus, the electron diffraction pattern indicatesthat the crystal structure of the CAC-OS includes a nanocrystal (nc)structure with no alignment in a plan-view direction and across-sectional direction.

Moreover, for example, it can be confirmed by EDX mapping obtained usingenergy dispersive X-ray spectroscopy (EDX) that the CAC-OS in theIn—Ga—Zn oxide has a composition in which regions including GaO_(X3) asa main component and regions including In_(X2)Zn_(Y2)O_(Z2) or InO_(X1)as a main component are unevenly distributed and mixed.

The CAC-OS has a structure different from that of an IGZO compound inwhich metal elements are evenly distributed, and has characteristicsdifferent from those of the IGZO compound. That is, the CAC-OS has acomposition in which regions including GaO_(X3) or the like as a maincomponent and regions including In_(X2)Zn_(Y2)O_(Z2) or InO_(X1) as amain component are phase-separated from each other, and the regionsincluding the respective elements as the main components form a mosaicpattern.

Here, a region including In_(X2)Zn_(Y2)O_(Z2) or InO_(X1) as a maincomponent is a region with higher conductivity than a region includingGaO_(X3) or the like as a main component. In other words, when carriersflow through regions including In_(X2)Zn_(Y2)O_(Z2) or InO_(X1) as amain component, the conductivity of a metal oxide is exhibited.Accordingly, when regions including In_(X2)Zn_(Y2)O_(Z2) or InO_(X1) asa main component are distributed in a metal oxide like a cloud, highfield-effect mobility (μ) can be achieved.

By contrast, a region including GaO_(X3) or the like as a main componentis a region with higher insulating property than a region includingIn_(X2)Zn_(Y2)O_(Z2) or InO_(X1) as a main component. In other words,when regions including GaO_(X3) or the like as a main component aredistributed in a metal oxide, leakage current can be suppressed andfavorable switching operation can be achieved.

Accordingly, when the CAC-OS is used in a semiconductor element, theinsulating property derived from GaO_(X3) or the like and theconductivity derived from In_(X2)Zn_(Y2)O_(Z2) or InO_(X1) complementeach other, whereby high on-state current (I_(on)) and high field-effectmobility (μ) can be achieved.

A semiconductor element using a CAC-OS has high reliability. Thus, theCAC-OS is suitably used in a variety of semiconductor devices typifiedby a display.

This embodiment can be combined with any of the other embodiments asappropriate.

Embodiment 4

In this embodiment, examples of an electronic device that can use asemiconductor device of one embodiment of the present invention will bedescribed.

FIG. 19A illustrates a biometric authentication device including ahousing 911, operation buttons 912, a sensor portion 913, and the like.When a hand or a finger is held over or put on the sensor portion 913, aform of vein can be recognized. The sensor portion 913 can also displayan image. The obtained data can be transmitted to a server by a wirelesscommunication unit 914 and compared with a database, so that anindividual can be specified. Furthermore, a security code or the likecan be input with the operation buttons.

The semiconductor device of one embodiment of the present invention isplaced directly under the sensor portion 913. Thus, the detectionsensitivity of the sensor portion 913 can be increased and ahigh-luminance image can be displayed on the sensor portion 913.

FIG. 19B illustrates a non-destructive inspection device including ahousing 921, an operation panel 922, a transfer mechanism 923, a monitor924, a sensor unit 925, and the like. Inspection members 926 aretransported to the position directly under the sensor unit 925 by thetransport mechanism 923. Images of the inspection members 926 arecaptured by the semiconductor device of one embodiment of the presentinvention provided in the sensor unit 925, and the captured images aredisplayed on the monitor 924. After that, the inspection members 926 aretransported to an exit of the housing 921 and a defective member isseparately collected.

The semiconductor device of one embodiment of the present invention isplaced directly under the sensor unit 925. Accordingly, the detectionsensitivity of the sensor unit 925 can be increased.

FIG. 19C illustrates a food-sorting device including a housing 931,operation buttons 932, a display portion 933, a light-blocking hood 934,and the like. Imaging is performed with the light-blocking hood 934,which is provided around a light-receiving portion, being in closecontact with a target inspection food such as a fruit, whereby a foreignsubstance or an insect mixed in the food, a cavity or rot inside thefood, and the like can be detected. In addition, sugar content, moisturecontent, and the like can also be detected from the intensity of thedetected infrared light or the like. With the food-sorting device,defective products and grades can be sorted and the harvest time can bedetermined.

The semiconductor device of one embodiment of the present invention canbe provided in the light-receiving portion. Accordingly, the lightdetection sensitivity of the light-receiving portion can be increased.Note that the structure illustrated in FIG. 19B may be used for thefood-sorting device. Alternatively, the structure illustrated in FIG.19C may be used for the non-destructive inspection device.

This embodiment can be combined with any of the other embodiments asappropriate.

Embodiment 5

In this embodiment, a market image where the semiconductor device of oneembodiment of the present invention can be used will be described.

<Market Image>

FIG. 20 illustrates a market image where the semiconductor device of oneembodiment of the present invention can be used. In FIG. 20, a region701 represents a product field (OS Display) applicable to a displayusing a transistor including an oxide semiconductor in a channelformation region; a region 702 represents a product field (OS LSIanalog) where an LSI (Large Scale Integration) using a transistorincluding an oxide semiconductor in a channel formation region can beapplied to an analog one; and a region 703 represents a product field(OS LSI digital) where an LSI using a transistor including an oxidesemiconductor in a channel formation region can be applied to a digitalone. The semiconductor device of one embodiment of the present inventioncan be favorably used in the three regions: the region 701, the region702, and the region 703 illustrated in FIG. 20, in other words, threebig markets.

In FIG. 20, a region 704 represents a region where the region 701 andthe region 702 overlap with each other; a region 705 represents a regionwhere the region 702 and the region 703 overlap with each other; aregion 706 represents a region where the region 701 and the region 703overlap with each other; and a region 707 represents a region where theregion 701, the region 702, and the region 703 overlap with one another.

In OS Display, an FET structure such as a bottom-gate OS FET (BG OSFET)or a top-gate OS FET (TG OS FET) can be favorably used. Note that thebottom-gate OS FET includes a channel-etched FET and achannel-protective FET. In addition, the top-gate OS FET includes a TGSA(Top Gate Self-Aligned) FET.

In OS LSI analog and OS LSI digital, a gate-last OS FET (GL OS FET) canbe favorably used, for example.

Note that the above-described transistors each include a single-gatetransistor with one gate electrode, a dual-gate transistor with two gateelectrodes, or a transistor with three or more gate electrodes. Amongdual-gate transistors, it is particularly preferable to use an S-channel(surrounded channel) transistor.

Note that in this specification and the like, an S-channel transistorrefers to a transistor with a structure in which a channel formationregion is electrically surrounded by the electric fields of one of apair of gate electrodes and the other thereof.

As products included in OS display (the region 701), products in whichan LCD (liquid crystal display), EL (Electro Luminescence), and an LED(Light Emitting Diode) are included as display elements can be given.Any of the above display elements is favorably combined with Q-Dot(Quantum Dot).

Note that in this embodiment, EL includes organic EL and inorganic EL.In addition, in this embodiment, LED includes a micro LED, a mini LED,and a macro LED. Note that in this specification and the like, alight-emitting diode with a chip size of 10000 μm² or less is referredto as a micro LED, a light-emitting diode with a chip size of greaterthan 10000 μm² and less than or equal to 1 mm² is referred to as a miniLED, and a light-emitting diode with a chip size of greater than 1 mm²is referred to as a macro LED, in some cases.

As products included in OS LSI analog (the region 702), a sound-sourceidentification device that covers a wide frequency range (e.g., anaudible sound with a frequency of 20 Hz to 20 kHz inclusive orultrasonic wave of 20 kHz or greater), a battery control device (abattery control IC, a battery protection IC, or a battery managementsystem), and the like can be given.

As products included in OS LSI digital (the region 703), a memorydevice, a CPU (Central Processing Unit) device, a GPU (GraphicsProcessing Unit) device, an FPGA (field-programmable gate array) device,a power device, a hybrid device in which an OS LSI and an Si LSI arestacked or mixed, a light-emitting element, and the like can be given.

As products included in the region 704, a display element including aninfrared ray sensor or a near-infrared ray sensor in a display region, asensor-equipped signal processing device including an OS FET, animplantable biosensor device, and the like can be given. As productsincluded in the region 705, a processing circuit including an A/D(Analog to Digital) conversion circuit or the like, an AI (ArtificialIntelligence) device including the processing circuit, and the like canbe given. As products included in the region 706, a display device usinga Pixel AI technology can be given, for example. Note that in thisspecification and the like, the Pixel AI technology refers to atechnology utilizing a memory composed of an OS FET or the like includedin a pixel circuit of a display.

As a product included in the region 707, a composite that combines avariety of products included in the region 701 to the region 706 can begiven.

As described above, the semiconductor device of one embodiment of thepresent invention can be applied to a variety of product fields, asillustrated in FIG. 20. That is, the semiconductor device of oneembodiment of the present invention can be applied to a lot of markets.

Note that the structures described in this embodiment can be implementedin combination with any of the other embodiments described in thisspecification and the like as appropriate.

This embodiment can be combined with any of the other embodiments asappropriate.

REFERENCE NUMERALS

-   10: pixel, 10B: pixel, 10G: pixel, 10IR: pixel, 10R: pixel, 11:    substrate, 12: photoelectric conversion element, 13: low-resistance    region, 14: conductive layer, 21: conductive layer, 22: conductive    layer, 23: conductive layer, 24: conductive layer, 30: substrate,    31: conductive layer, 32: insulating layer, 33: insulating layer,    34: low-resistance region, 40: light-emitting element, 41:    conductive layer, 42: EL layer, 42 a: EL layer, 42 b: EL layer, 42    c: EL layer, 43: conductive layer, 44: charge generation layer, 44    a: charge generation layer, 44 b: charge generation layer, 45:    conductive layer, 46: active layer, 50: substrate, 51: filter, 51B:    filter, 51G: filter, 51IR: filter, 51R: filter, 52: sealing layer,    53: filter, 54: microlens, 55: microlens, 56: light control layer,    60: substrate, 61: layer, 62: layer, 63: layer, 64: layer, 71:    hole-injection layer, 72: hole-transport layer, 73: light-emitting    layer, 74: electron-transport layer, 75: electron-injection layer,    80: insulating layer, 81: insulating layer, 82: insulating layer,    83: insulating layer, 84: insulating layer, 85: insulating layer,    86: insulating layer, 87: insulating layer, 100: imaging circuit,    101: transistor, 102: transistor, 103: transistor, 104: transistor,    105: capacitor, 111: wiring, 112: wiring, 114: wiring, 121: wiring,    122: wiring, 124: wiring, 125: wiring, 130: display circuit, 131:    transistor, 132: transistor, 133: transistor, 134: capacitor, 141:    wiring, 142: wiring, 143: wiring, 144: wiring, 145: wiring, 151:    pixel array, 152: gate driver circuit, 153: source driver circuit,    154: data generation circuit, 155: wiring, 201: gate electrode, 202:    gate insulating layer, 203: source region, 204: drain region, 205:    source electrode, 206: drain electrode, 207: metal oxide layer, 208:    metal oxide layer, 210: channel formation region, 235: back gate    electrode, 610: arithmetic device, 611: arithmetic portion, 612:    memory portion, 620: input/output device, 660: reading portion, 670:    electric lock, 701: region, 702: region, 703: region, 704: region,    705: region, 706: region, 707: region, 911: housing, 912: operation    button, 913: sensor portion, 914: wireless communication unit, 921:    housing, 922: operation panel, 923: transfer mechanism, 924:    monitor, 925: sensor unit, 926: inspection member, 931: housing,    932: operation button, 933: display portion, 934: light-blocking    hood

1. An authentication system comprising: an arithmetic device; and aninput/output device, wherein the arithmetic device supplies firstcontrol data and second control data, wherein the arithmetic device issupplied with a sensor signal, wherein the input/output device comprisesan electric lock and a reading portion, wherein the electric lock isunlocked on the basis of the second control data, wherein the readingportion is supplied with the first control data and supplies the sensorsignal, wherein the reading portion comprises a light-emitting elementand a pixel array, wherein the light-emitting element emits lightcomprising infrared rays, wherein the pixel array comprises pixels,wherein the pixels each comprise an imaging circuit and a photoelectricconversion element, wherein the imaging circuit is electricallyconnected to the photoelectric conversion element, wherein the imagingcircuit comprises a transistor, and wherein the transistor comprises anoxide semiconductor film.
 2. The authentication system according toclaim 1, wherein the arithmetic device comprises an arithmetic portionand a memory portion, wherein the memory portion stores a program and afirst database, wherein the arithmetic portion extracts a feature valuefrom the sensor signal on the basis of the program, wherein thearithmetic portion examines the feature value using the first database,and wherein the arithmetic portion supplies the second control data onthe basis of an examination result.
 3. The authentication systemaccording to claim 2, wherein the memory portion stores a seconddatabase, and wherein the arithmetic portion records an unlockinghistory in the second database on the basis of the examination result.4. The authentication system according to claim 1, wherein the pixelcomprises a first layer and a second layer, wherein the first layercomprises a first transistor and a second transistor, wherein the secondlayer comprises a light-emitting element and a photoelectric conversionelement, and wherein one of a source and a drain of the first transistoris electrically connected to one electrode of the light-emittingelement, and one of a source and a drain of the second transistor iselectrically connected to one electrode of the photoelectric conversionelement.
 5. The authentication system according to claim 1, wherein theoxide semiconductor film comprises In, Zn, and M (M is Al, Ti, Ga, Sn,Y, Zr, La, Ce, Nd, or Hf).
 6. A method for recording an unlockinghistory, comprising a first step to a seventh step, wherein in the firststep, imaging is performed to obtain a sensor signal, wherein in thesecond step, a program proceeds to the third step in the case where achange exceeding a predetermine level is observed in the sensor signaland the program proceeds to the first step in the case where only achange less than or equal to the predetermined level is observed,wherein in the third step, imaging is performed to obtain a sensorsignal, wherein in the fourth step, a feature value is extracted fromthe sensor signal which was obtained in the third step, wherein in thefifth step, the feature value is examined using a first database, andthe program proceeds to the sixth step in the case where the firstdatabase comprises data matching the feature value and the programproceeds to the first step in the case where the first databasecomprises no data matching the feature value, wherein in the sixth step,second control data is supplied to unlock an electric lock, and whereinin the seventh step, the unlocking history is recorded in a seconddatabase.
 7. The authentication system according to claim 2, wherein thepixel comprises a first layer and a second layer, wherein the firstlayer comprises a first transistor and a second transistor, wherein thesecond layer comprises a light-emitting element and a photoelectricconversion element, and wherein one of a source and a drain of the firsttransistor is electrically connected to one electrode of thelight-emitting element, and one of a source and a drain of the secondtransistor is electrically connected to one electrode of thephotoelectric conversion element.
 8. The authentication system accordingto claim 2, wherein the oxide semiconductor film comprises In, Zn, and M(M is Al, Ti, Ga, Sn, Y, Zr, La, Ce, Nd, or Hf).